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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [xen staging] x86/xstate: Cross-check dynamic XSTATE sizes at boot
commit d31a111940de5431c8bf465b1d38b89f1130a24b
Author: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
AuthorDate: Fri Feb 21 17:56:57 2020 +0000
Commit: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
CommitDate: Wed Jun 19 13:00:06 2024 +0100
x86/xstate: Cross-check dynamic XSTATE sizes at boot
Right now, xstate_ctxt_size() performs a cross-check of size with CPUID in
for
every call. This is expensive, being used for domain create/migrate, as
well
as to service certain guest CPUID instructions.
Instead, arrange to check the sizes once at boot. See the code comments for
details. Right now, it just checks hardware against the algorithm
expectations. Later patches will cross-check Xen's XSTATE calculations too.
Introduce more X86_XCR0_* and X86_XSS_* constants CPUID bits. This is to
maximise coverage in the sanity check, even if we don't expect to
use/virtualise some of these features any time soon. Leave HDC and HWP
alone
for now; we don't have CPUID bits from them stored nicely.
Only perform the cross-checks when SELF_TESTS are active. It's only
developers or new hardware liable to trip these checks, and Xen at least
tracks "maximum value ever seen in xcr0" for the lifetime of the VM, which
we
don't want to be tickling in the general case.
Signed-off-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
Release-Acked-by: Oleksii Kurochko <oleksii.kurochko@xxxxxxxxx>
---
xen/arch/x86/include/asm/x86-defns.h | 25 +++-
xen/arch/x86/xstate.c | 170 ++++++++++++++++++++++++++++
xen/include/public/arch-x86/cpufeatureset.h | 3 +
3 files changed, 197 insertions(+), 1 deletion(-)
diff --git a/xen/arch/x86/include/asm/x86-defns.h
b/xen/arch/x86/include/asm/x86-defns.h
index 48d7a3b7af..d7602ab225 100644
--- a/xen/arch/x86/include/asm/x86-defns.h
+++ b/xen/arch/x86/include/asm/x86-defns.h
@@ -77,7 +77,7 @@
#define X86_CR4_PKS 0x01000000 /* Protection Key Supervisor */
/*
- * XSTATE component flags in XCR0
+ * XSTATE component flags in XCR0 | MSR_XSS
*/
#define X86_XCR0_FP_POS 0
#define X86_XCR0_FP (1ULL << X86_XCR0_FP_POS)
@@ -95,11 +95,34 @@
#define X86_XCR0_ZMM (1ULL << X86_XCR0_ZMM_POS)
#define X86_XCR0_HI_ZMM_POS 7
#define X86_XCR0_HI_ZMM (1ULL << X86_XCR0_HI_ZMM_POS)
+#define X86_XSS_PROC_TRACE (_AC(1, ULL) << 8)
#define X86_XCR0_PKRU_POS 9
#define X86_XCR0_PKRU (1ULL << X86_XCR0_PKRU_POS)
+#define X86_XSS_PASID (_AC(1, ULL) << 10)
+#define X86_XSS_CET_U (_AC(1, ULL) << 11)
+#define X86_XSS_CET_S (_AC(1, ULL) << 12)
+#define X86_XSS_HDC (_AC(1, ULL) << 13)
+#define X86_XSS_UINTR (_AC(1, ULL) << 14)
+#define X86_XSS_LBR (_AC(1, ULL) << 15)
+#define X86_XSS_HWP (_AC(1, ULL) << 16)
+#define X86_XCR0_TILE_CFG (_AC(1, ULL) << 17)
+#define X86_XCR0_TILE_DATA (_AC(1, ULL) << 18)
#define X86_XCR0_LWP_POS 62
#define X86_XCR0_LWP (1ULL << X86_XCR0_LWP_POS)
+#define X86_XCR0_STATES \
+ (X86_XCR0_FP | X86_XCR0_SSE | X86_XCR0_YMM | X86_XCR0_BNDREGS | \
+ X86_XCR0_BNDCSR | X86_XCR0_OPMASK | X86_XCR0_ZMM | \
+ X86_XCR0_HI_ZMM | X86_XCR0_PKRU | X86_XCR0_TILE_CFG | \
+ X86_XCR0_TILE_DATA | \
+ X86_XCR0_LWP)
+
+#define X86_XSS_STATES \
+ (X86_XSS_PROC_TRACE | X86_XSS_PASID | X86_XSS_CET_U | \
+ X86_XSS_CET_S | X86_XSS_HDC | X86_XSS_UINTR | X86_XSS_LBR | \
+ X86_XSS_HWP | \
+ 0)
+
/*
* Debug status flags in DR6.
*
diff --git a/xen/arch/x86/xstate.c b/xen/arch/x86/xstate.c
index 7578814796..408d9dd108 100644
--- a/xen/arch/x86/xstate.c
+++ b/xen/arch/x86/xstate.c
@@ -604,9 +604,176 @@ static bool valid_xcr0(uint64_t xcr0)
if ( !(xcr0 & X86_XCR0_BNDREGS) != !(xcr0 & X86_XCR0_BNDCSR) )
return false;
+ /* TILECFG and TILEDATA must be the same. */
+ if ( !(xcr0 & X86_XCR0_TILE_CFG) != !(xcr0 & X86_XCR0_TILE_DATA) )
+ return false;
+
return true;
}
+struct xcheck_state {
+ uint64_t states;
+ uint32_t uncomp_size;
+ uint32_t comp_size;
+};
+
+static void __init check_new_xstate(struct xcheck_state *s, uint64_t new)
+{
+ uint32_t hw_size;
+
+ BUILD_BUG_ON(X86_XCR0_STATES & X86_XSS_STATES);
+
+ BUG_ON(new <= s->states); /* States strictly increase by index. */
+ BUG_ON(s->states & new); /* States only accumulate. */
+ BUG_ON(!valid_xcr0(s->states | new)); /* Xen thinks it's a good value. */
+ BUG_ON(new & ~(X86_XCR0_STATES | X86_XSS_STATES)); /* Known state. */
+ BUG_ON((new & X86_XCR0_STATES) &&
+ (new & X86_XSS_STATES)); /* User or supervisor, not both. */
+
+ s->states |= new;
+ if ( new & X86_XCR0_STATES )
+ {
+ if ( !set_xcr0(s->states & X86_XCR0_STATES) )
+ BUG();
+ }
+ else
+ set_msr_xss(s->states & X86_XSS_STATES);
+
+ /*
+ * Check the uncompressed size. First ask hardware.
+ */
+ hw_size = cpuid_count_ebx(0xd, 0);
+
+ if ( new & X86_XSS_STATES )
+ {
+ /*
+ * Supervisor states don't exist in an uncompressed image, so check
+ * that the uncompressed size doesn't change. Otherwise...
+ */
+ if ( hw_size != s->uncomp_size )
+ panic("XSTATE 0x%016"PRIx64", new sup bits {%63pbl}, uncompressed
hw size %#x != prev size %#x\n",
+ s->states, &new, hw_size, s->uncomp_size);
+ }
+ else
+ {
+ /*
+ * ... some user XSTATEs are out-of-order and fill in prior holes.
+ * The best check we make is that the size never decreases.
+ */
+ if ( hw_size < s->uncomp_size )
+ panic("XSTATE 0x%016"PRIx64", new bits {%63pbl}, uncompressed hw
size %#x < prev size %#x\n",
+ s->states, &new, hw_size, s->uncomp_size);
+ }
+
+ s->uncomp_size = hw_size;
+
+ /*
+ * Check the compressed size, if available.
+ */
+ hw_size = cpuid_count_ebx(0xd, 1);
+
+ if ( cpu_has_xsavec )
+ {
+ /*
+ * All components strictly appear in index order, irrespective of
+ * whether they're user or supervisor. As each component also has
+ * non-zero size, the accumulated size should strictly increase.
+ */
+ if ( hw_size <= s->comp_size )
+ panic("XSTATE 0x%016"PRIx64", new bits {%63pbl}, compressed hw
size %#x <= prev size %#x\n",
+ s->states, &new, hw_size, s->comp_size);
+
+ s->comp_size = hw_size;
+ }
+ else if ( hw_size ) /* Compressed size reported, but no XSAVEC ? */
+ {
+ static bool once;
+
+ if ( !once )
+ {
+ WARN();
+ once = true;
+ }
+ }
+}
+
+/*
+ * The {un,}compressed XSTATE sizes are reported by dynamic CPUID value, based
+ * on the current %XCR0 and MSR_XSS values. The exact layout is also feature
+ * and vendor specific. Cross-check Xen's understanding against real hardware
+ * on boot.
+ *
+ * Testing every combination is prohibitive, so we use a partial approach.
+ * Starting with nothing active, we add new XSTATEs and check that the CPUID
+ * dynamic values never decreases.
+ */
+static void __init noinline xstate_check_sizes(void)
+{
+ uint64_t old_xcr0 = get_xcr0();
+ uint64_t old_xss = get_msr_xss();
+ struct xcheck_state s = {};
+
+ /*
+ * User and supervisor XSTATEs, increasing by index.
+ *
+ * Chronologically, Intel and AMD had identical layouts for AVX (YMM).
+ * AMD introduced LWP in Fam15h, following immediately on from YMM. Intel
+ * left an LWP-shaped hole when adding MPX (BND{CSR,REGS}) in Skylake.
+ * AMD removed LWP in Fam17h, putting PKRU in the same space, breaking
+ * layout compatibility with Intel and having a knock-on effect on all
+ * subsequent states.
+ */
+ check_new_xstate(&s, X86_XCR0_SSE | X86_XCR0_FP);
+
+ if ( cpu_has_avx )
+ check_new_xstate(&s, X86_XCR0_YMM);
+
+ if ( cpu_has_mpx )
+ check_new_xstate(&s, X86_XCR0_BNDCSR | X86_XCR0_BNDREGS);
+
+ if ( cpu_has_avx512f )
+ check_new_xstate(&s, X86_XCR0_HI_ZMM | X86_XCR0_ZMM | X86_XCR0_OPMASK);
+
+ /*
+ * Intel Broadwell has Processor Trace but no XSAVES. There doesn't
+ * appear to have been a new enumeration when X86_XSS_PROC_TRACE was
+ * introduced in Skylake.
+ */
+ if ( cpu_has_xsaves && cpu_has_proc_trace )
+ check_new_xstate(&s, X86_XSS_PROC_TRACE);
+
+ if ( cpu_has_pku )
+ check_new_xstate(&s, X86_XCR0_PKRU);
+
+ if ( cpu_has_xsaves && boot_cpu_has(X86_FEATURE_ENQCMD) )
+ check_new_xstate(&s, X86_XSS_PASID);
+
+ if ( cpu_has_xsaves && (boot_cpu_has(X86_FEATURE_CET_SS) ||
+ boot_cpu_has(X86_FEATURE_CET_IBT)) )
+ {
+ check_new_xstate(&s, X86_XSS_CET_U);
+ check_new_xstate(&s, X86_XSS_CET_S);
+ }
+
+ if ( cpu_has_xsaves && boot_cpu_has(X86_FEATURE_UINTR) )
+ check_new_xstate(&s, X86_XSS_UINTR);
+
+ if ( cpu_has_xsaves && boot_cpu_has(X86_FEATURE_ARCH_LBR) )
+ check_new_xstate(&s, X86_XSS_LBR);
+
+ if ( boot_cpu_has(X86_FEATURE_AMX_TILE) )
+ check_new_xstate(&s, X86_XCR0_TILE_DATA | X86_XCR0_TILE_CFG);
+
+ if ( boot_cpu_has(X86_FEATURE_LWP) )
+ check_new_xstate(&s, X86_XCR0_LWP);
+
+ /* Restore old state now the test is done. */
+ if ( !set_xcr0(old_xcr0) )
+ BUG();
+ if ( cpu_has_xsaves )
+ set_msr_xss(old_xss);
+}
+
/* Collect the information of processor's extended state */
void xstate_init(struct cpuinfo_x86 *c)
{
@@ -683,6 +850,9 @@ void xstate_init(struct cpuinfo_x86 *c)
if ( setup_xstate_features(bsp) && bsp )
BUG();
+
+ if ( IS_ENABLED(CONFIG_SELF_TESTS) && bsp )
+ xstate_check_sizes();
}
int validate_xstate(const struct domain *d, uint64_t xcr0, uint64_t xcr0_accum,
diff --git a/xen/include/public/arch-x86/cpufeatureset.h
b/xen/include/public/arch-x86/cpufeatureset.h
index 6627453e39..d9eba5e9a7 100644
--- a/xen/include/public/arch-x86/cpufeatureset.h
+++ b/xen/include/public/arch-x86/cpufeatureset.h
@@ -266,6 +266,7 @@ XEN_CPUFEATURE(IBPB_RET, 8*32+30) /*A IBPB clears
RSB/RAS too. */
XEN_CPUFEATURE(AVX512_4VNNIW, 9*32+ 2) /*A AVX512 Neural Network Instructions
*/
XEN_CPUFEATURE(AVX512_4FMAPS, 9*32+ 3) /*A AVX512 Multiply Accumulation
Single Precision */
XEN_CPUFEATURE(FSRM, 9*32+ 4) /*A Fast Short REP MOVS */
+XEN_CPUFEATURE(UINTR, 9*32+ 5) /* User-mode Interrupts */
XEN_CPUFEATURE(AVX512_VP2INTERSECT, 9*32+8) /*a VP2INTERSECT{D,Q} insns */
XEN_CPUFEATURE(SRBDS_CTRL, 9*32+ 9) /* MSR_MCU_OPT_CTRL and
RNGDS_MITG_DIS. */
XEN_CPUFEATURE(MD_CLEAR, 9*32+10) /*!A| VERW clears microarchitectural
buffers */
@@ -274,8 +275,10 @@ XEN_CPUFEATURE(TSX_FORCE_ABORT, 9*32+13) /*
MSR_TSX_FORCE_ABORT.RTM_ABORT */
XEN_CPUFEATURE(SERIALIZE, 9*32+14) /*A SERIALIZE insn */
XEN_CPUFEATURE(HYBRID, 9*32+15) /* Heterogeneous platform */
XEN_CPUFEATURE(TSXLDTRK, 9*32+16) /*a TSX load tracking suspend/resume
insns */
+XEN_CPUFEATURE(ARCH_LBR, 9*32+19) /* Architectural Last Branch Record */
XEN_CPUFEATURE(CET_IBT, 9*32+20) /* CET - Indirect Branch Tracking */
XEN_CPUFEATURE(AVX512_FP16, 9*32+23) /*A AVX512 FP16 instructions */
+XEN_CPUFEATURE(AMX_TILE, 9*32+24) /* AMX Tile architecture */
XEN_CPUFEATURE(IBRSB, 9*32+26) /*A IBRS and IBPB support (used by
Intel) */
XEN_CPUFEATURE(STIBP, 9*32+27) /*A STIBP */
XEN_CPUFEATURE(L1D_FLUSH, 9*32+28) /*S MSR_FLUSH_CMD and L1D flush. */
--
generated by git-patchbot for /home/xen/git/xen.git#staging
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