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[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] [PATCH v3 2/2] x86/mm: merge ptwr and mmio_ro page fault handlers
Provide a unified entry to avoid going through pte look-up, decode and
emulation cycle more than necessary. The path taken is determined by
the faulting address.
Note that the order of checks is changed in the new function, but the
order of the checks is performed shouldn't matter.
The sole caller is changed to use the new function.
No functional change.
Signed-off-by: Wei Liu <wei.liu2@xxxxxxxxxx>
---
Cc: Jan Beulich <jbeulich@xxxxxxxx>
Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>
v3:
1. place new function in the original location
2. remove goto out in ptwr_do_page_fault
3. add const to struct domain in mmio_ro_do_page_fault
4. remove the vcpu parameter in pv_ro_page_fault and use current->domain
v2: rebase and (sorta) merge Andrew's changes
Dom0 boots fine. XTF is happy with this change. Let me know if more
tests can be done.
---
xen/arch/x86/mm.c | 210 ++++++++++++++++++++---------------------------
xen/arch/x86/traps.c | 20 +++--
xen/include/asm-x86/mm.h | 5 +-
3 files changed, 100 insertions(+), 135 deletions(-)
diff --git a/xen/arch/x86/mm.c b/xen/arch/x86/mm.c
index 8831f06605..4d76319170 100644
--- a/xen/arch/x86/mm.c
+++ b/xen/arch/x86/mm.c
@@ -5177,86 +5177,40 @@ static const struct x86_emulate_ops ptwr_emulate_ops = {
};
/* Write page fault handler: check if guest is trying to modify a PTE. */
-int ptwr_do_page_fault(struct vcpu *v, unsigned long addr,
- struct cpu_user_regs *regs)
+static int ptwr_do_page_fault(struct x86_emulate_ctxt *ctxt,
+ unsigned long addr, l1_pgentry_t pte)
{
- struct domain *d = v->domain;
- struct page_info *page;
- l1_pgentry_t pte;
- struct ptwr_emulate_ctxt ptwr_ctxt;
- struct x86_emulate_ctxt ctxt = {
- .regs = regs,
- .vendor = d->arch.cpuid->x86_vendor,
- .addr_size = is_pv_32bit_domain(d) ? 32 : BITS_PER_LONG,
- .sp_size = is_pv_32bit_domain(d) ? 32 : BITS_PER_LONG,
- .lma = !is_pv_32bit_domain(d),
- .data = &ptwr_ctxt,
+ struct ptwr_emulate_ctxt ptwr_ctxt = {
+ .cr2 = addr,
+ .pte = pte,
};
+ struct page_info *page;
int rc;
- /* Attempt to read the PTE that maps the VA being accessed. */
- pte = guest_get_eff_l1e(addr);
-
- /* We are looking only for read-only mappings of p.t. pages. */
- if ( ((l1e_get_flags(pte) & (_PAGE_PRESENT|_PAGE_RW)) != _PAGE_PRESENT) ||
- rangeset_contains_singleton(mmio_ro_ranges, l1e_get_pfn(pte)) ||
- !get_page_from_mfn(l1e_get_mfn(pte), d) )
- goto bail;
+ if ( !get_page_from_mfn(l1e_get_mfn(pte), current->domain) )
+ return X86EMUL_UNHANDLEABLE;
page = l1e_get_page(pte);
if ( !page_lock(page) )
{
put_page(page);
- goto bail;
+ return X86EMUL_UNHANDLEABLE;
}
if ( (page->u.inuse.type_info & PGT_type_mask) != PGT_l1_page_table )
{
page_unlock(page);
put_page(page);
- goto bail;
+ return X86EMUL_UNHANDLEABLE;
}
- ptwr_ctxt.cr2 = addr;
- ptwr_ctxt.pte = pte;
-
- rc = x86_emulate(&ctxt, &ptwr_emulate_ops);
+ ctxt->data = &ptwr_ctxt;
+ rc = x86_emulate(ctxt, &ptwr_emulate_ops);
page_unlock(page);
put_page(page);
- switch ( rc )
- {
- case X86EMUL_EXCEPTION:
- /*
- * This emulation only covers writes to pagetables which are marked
- * read-only by Xen. We tolerate #PF (in case a concurrent pagetable
- * update has succeeded on a different vcpu). Anything else is an
- * emulation bug, or a guest playing with the instruction stream under
- * Xen's feet.
- */
- if ( ctxt.event.type == X86_EVENTTYPE_HW_EXCEPTION &&
- ctxt.event.vector == TRAP_page_fault )
- pv_inject_event(&ctxt.event);
- else
- gdprintk(XENLOG_WARNING,
- "Unexpected event (type %u, vector %#x) from emulation\n",
- ctxt.event.type, ctxt.event.vector);
-
- /* Fallthrough */
- case X86EMUL_OKAY:
-
- if ( ctxt.retire.singlestep )
- pv_inject_hw_exception(TRAP_debug, X86_EVENT_NO_EC);
-
- /* Fallthrough */
- case X86EMUL_RETRY:
- perfc_incr(ptwr_emulations);
- return EXCRET_fault_fixed;
- }
-
- bail:
- return 0;
+ return rc;
}
/*************************
@@ -5332,80 +5286,28 @@ static const struct x86_emulate_ops mmcfg_intercept_ops
= {
};
/* Check if guest is trying to modify a r/o MMIO page. */
-int mmio_ro_do_page_fault(struct vcpu *v, unsigned long addr,
- struct cpu_user_regs *regs)
+static int mmio_ro_do_page_fault(struct x86_emulate_ctxt *ctxt,
+ unsigned long addr, l1_pgentry_t pte)
{
- l1_pgentry_t pte;
- unsigned long mfn;
- unsigned int addr_size = is_pv_32bit_vcpu(v) ? 32 : BITS_PER_LONG;
struct mmio_ro_emulate_ctxt mmio_ro_ctxt = { .cr2 = addr };
- struct x86_emulate_ctxt ctxt = {
- .regs = regs,
- .vendor = v->domain->arch.cpuid->x86_vendor,
- .addr_size = addr_size,
- .sp_size = addr_size,
- .lma = !is_pv_32bit_vcpu(v),
- .data = &mmio_ro_ctxt,
- };
- int rc;
+ mfn_t mfn = l1e_get_mfn(pte);
- /* Attempt to read the PTE that maps the VA being accessed. */
- pte = guest_get_eff_l1e(addr);
-
- /* We are looking only for read-only mappings of MMIO pages. */
- if ( ((l1e_get_flags(pte) & (_PAGE_PRESENT|_PAGE_RW)) != _PAGE_PRESENT) )
- return 0;
-
- mfn = l1e_get_pfn(pte);
- if ( mfn_valid(_mfn(mfn)) )
+ if ( mfn_valid(mfn) )
{
- struct page_info *page = mfn_to_page(_mfn(mfn));
- struct domain *owner = page_get_owner_and_reference(page);
+ struct page_info *page = mfn_to_page(mfn);
+ const struct domain *owner = page_get_owner_and_reference(page);
if ( owner )
put_page(page);
if ( owner != dom_io )
- return 0;
+ return X86EMUL_UNHANDLEABLE;
}
- if ( !rangeset_contains_singleton(mmio_ro_ranges, mfn) )
- return 0;
-
- if ( pci_ro_mmcfg_decode(mfn, &mmio_ro_ctxt.seg, &mmio_ro_ctxt.bdf) )
- rc = x86_emulate(&ctxt, &mmcfg_intercept_ops);
+ ctxt->data = &mmio_ro_ctxt;
+ if ( pci_ro_mmcfg_decode(mfn_x(mfn), &mmio_ro_ctxt.seg, &mmio_ro_ctxt.bdf)
)
+ return x86_emulate(ctxt, &mmcfg_intercept_ops);
else
- rc = x86_emulate(&ctxt, &mmio_ro_emulate_ops);
-
- switch ( rc )
- {
- case X86EMUL_EXCEPTION:
- /*
- * This emulation only covers writes to MMCFG space or read-only MFNs.
- * We tolerate #PF (from hitting an adjacent page or a successful
- * concurrent pagetable update). Anything else is an emulation bug,
- * or a guest playing with the instruction stream under Xen's feet.
- */
- if ( ctxt.event.type == X86_EVENTTYPE_HW_EXCEPTION &&
- ctxt.event.vector == TRAP_page_fault )
- pv_inject_event(&ctxt.event);
- else
- gdprintk(XENLOG_WARNING,
- "Unexpected event (type %u, vector %#x) from emulation\n",
- ctxt.event.type, ctxt.event.vector);
-
- /* Fallthrough */
- case X86EMUL_OKAY:
-
- if ( ctxt.retire.singlestep )
- pv_inject_hw_exception(TRAP_debug, X86_EVENT_NO_EC);
-
- /* Fallthrough */
- case X86EMUL_RETRY:
- perfc_incr(mmio_ro_emulations);
- return EXCRET_fault_fixed;
- }
-
- return 0;
+ return x86_emulate(ctxt, &mmio_ro_emulate_ops);
}
void *alloc_xen_pagetable(void)
@@ -6439,6 +6341,70 @@ void write_32bit_pse_identmap(uint32_t *l2)
_PAGE_ACCESSED | _PAGE_DIRTY | _PAGE_PSE);
}
+int pv_ro_page_fault(unsigned long addr, struct cpu_user_regs *regs)
+{
+ l1_pgentry_t pte;
+ const struct domain *currd = current->domain;
+ unsigned int addr_size = is_pv_32bit_domain(currd) ? 32 : BITS_PER_LONG;
+ struct x86_emulate_ctxt ctxt = {
+ .regs = regs,
+ .vendor = currd->arch.cpuid->x86_vendor,
+ .addr_size = addr_size,
+ .sp_size = addr_size,
+ .lma = addr_size > 32,
+ };
+ int rc;
+ bool mmio_ro;
+
+ /* Attempt to read the PTE that maps the VA being accessed. */
+ pte = guest_get_eff_l1e(addr);
+
+ /* We are only looking for read-only mappings */
+ if ( ((l1e_get_flags(pte) & (_PAGE_PRESENT | _PAGE_RW)) != _PAGE_PRESENT) )
+ return 0;
+
+ mmio_ro = rangeset_contains_singleton(mmio_ro_ranges, l1e_get_pfn(pte));
+ if ( mmio_ro )
+ rc = mmio_ro_do_page_fault(&ctxt, addr, pte);
+ else
+ rc = ptwr_do_page_fault(&ctxt, addr, pte);
+
+ switch ( rc )
+ {
+ case X86EMUL_EXCEPTION:
+ /*
+ * This emulation covers writes to:
+ * - L1 pagetables.
+ * - MMCFG space or read-only MFNs.
+ * We tolerate #PF (from hitting an adjacent page or a successful
+ * concurrent pagetable update). Anything else is an emulation bug,
+ * or a guest playing with the instruction stream under Xen's feet.
+ */
+ if ( ctxt.event.type == X86_EVENTTYPE_HW_EXCEPTION &&
+ ctxt.event.vector == TRAP_page_fault )
+ pv_inject_event(&ctxt.event);
+ else
+ gdprintk(XENLOG_WARNING,
+ "Unexpected event (type %u, vector %#x) from emulation\n",
+ ctxt.event.type, ctxt.event.vector);
+
+ /* Fallthrough */
+ case X86EMUL_OKAY:
+ if ( ctxt.retire.singlestep )
+ pv_inject_hw_exception(TRAP_debug, X86_EVENT_NO_EC);
+
+ /* Fallthrough */
+ case X86EMUL_RETRY:
+ if ( mmio_ro )
+ perfc_incr(mmio_ro_emulations);
+ else
+ perfc_incr(ptwr_emulations);
+ return EXCRET_fault_fixed;
+ }
+
+ return 0;
+}
+
/*
* Local variables:
* mode: C
diff --git a/xen/arch/x86/traps.c b/xen/arch/x86/traps.c
index f525fa28d3..6091f239ce 100644
--- a/xen/arch/x86/traps.c
+++ b/xen/arch/x86/traps.c
@@ -1308,16 +1308,18 @@ static int fixup_page_fault(unsigned long addr, struct
cpu_user_regs *regs)
!(regs->error_code & (PFEC_reserved_bit | PFEC_insn_fetch)) &&
(regs->error_code & PFEC_write_access) )
{
- if ( VM_ASSIST(d, writable_pagetables) &&
- /* Do not check if access-protection fault since the page may
- legitimately be not present in shadow page tables */
- (paging_mode_enabled(d) ||
- (regs->error_code & PFEC_page_present)) &&
- ptwr_do_page_fault(v, addr, regs) )
- return EXCRET_fault_fixed;
+ bool ptwr, mmio_ro;
+
+ ptwr = VM_ASSIST(d, writable_pagetables) &&
+ /* Do not check if access-protection fault since the page may
+ legitimately be not present in shadow page tables */
+ (paging_mode_enabled(d) ||
+ (regs->error_code & PFEC_page_present));
+
+ mmio_ro = is_hardware_domain(d) &&
+ (regs->error_code & PFEC_page_present);
- if ( is_hardware_domain(d) && (regs->error_code & PFEC_page_present) &&
- mmio_ro_do_page_fault(v, addr, regs) )
+ if ( (ptwr || mmio_ro) && pv_ro_page_fault(addr, regs) )
return EXCRET_fault_fixed;
}
diff --git a/xen/include/asm-x86/mm.h b/xen/include/asm-x86/mm.h
index 4c03a33e79..97647dc401 100644
--- a/xen/include/asm-x86/mm.h
+++ b/xen/include/asm-x86/mm.h
@@ -511,10 +511,7 @@ extern int mmcfg_intercept_write(enum x86_segment seg,
int pv_emul_cpuid(uint32_t leaf, uint32_t subleaf,
struct cpuid_leaf *res, struct x86_emulate_ctxt *ctxt);
-int ptwr_do_page_fault(struct vcpu *, unsigned long,
- struct cpu_user_regs *);
-int mmio_ro_do_page_fault(struct vcpu *, unsigned long,
- struct cpu_user_regs *);
+int pv_ro_page_fault(unsigned long, struct cpu_user_regs *);
int audit_adjust_pgtables(struct domain *d, int dir, int noisy);
--
2.11.0
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