[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [PATCH V6 22/24] xen/arm: Add mapcache invalidation handling
From: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx> We need to send mapcache invalidation request to qemu/demu everytime the page gets removed from a guest. At the moment, the Arm code doesn't explicitely remove the existing mapping before inserting the new mapping. Instead, this is done implicitely by __p2m_set_entry(). First of all we need to recognize a case when the "freed" entry contains some RAM page in order to set the corresponding flag. The most suitable place to do this is p2m_free_entry(), there we can find the correct leaf type. The invalidation request will be sent in do_trap_hypercall() later on. Taking into the account the following the do_trap_hypercall() is the best place to send invalidation request: - The only way a guest can modify its P2M on Arm is via an hypercall - When sending the invalidation request, the vCPU will be blocked until all the IOREQ servers have acknowledged the invalidation Signed-off-by: Oleksandr Tyshchenko <oleksandr_tyshchenko@xxxxxxxx> CC: Julien Grall <julien.grall@xxxxxxx> Reviewed-by: Stefano Stabellini <sstabellini@xxxxxxxxxx> [On Arm only] Tested-by: Wei Chen <Wei.Chen@xxxxxxx> --- Please note, this is a split/cleanup/hardening of Julien's PoC: "Add support for Guest IO forwarding to a device emulator" *** Please note, this patch depends on the following which is on review: https://patchwork.kernel.org/patch/11803383/ This patch is on par with x86 code (whether it is buggy or not). If there is a need to improve/harden something, this can be done on a follow-up. *** Changes V1 -> V2: - new patch, some changes were derived from (+ new explanation): xen/ioreq: Make x86's invalidate qemu mapcache handling common - put setting of the flag into __p2m_set_entry() - clarify the conditions when the flag should be set - use domain_has_ioreq_server() - update do_trap_hypercall() by adding local variable Changes V2 -> V3: - update patch description - move check to p2m_free_entry() - add a comment - use "curr" instead of "v" in do_trap_hypercall() Changes V3 -> V4: - update patch description - re-order check in p2m_free_entry() to call domain_has_ioreq_server() only if p2m->domain == current->domain - add a comment in do_trap_hypercall() Changes V4 -> V5: - add Stefano's R-b - update comment in do_trap_hypercall() Changes V5 -> V6: - update comment in p2m_free_entry() and patch description --- --- xen/arch/arm/p2m.c | 25 +++++++++++++++++-------- xen/arch/arm/traps.c | 20 +++++++++++++++++--- 2 files changed, 34 insertions(+), 11 deletions(-) diff --git a/xen/arch/arm/p2m.c b/xen/arch/arm/p2m.c index d41c4fa..6895804 100644 --- a/xen/arch/arm/p2m.c +++ b/xen/arch/arm/p2m.c @@ -1,6 +1,7 @@ #include <xen/cpu.h> #include <xen/domain_page.h> #include <xen/iocap.h> +#include <xen/ioreq.h> #include <xen/lib.h> #include <xen/sched.h> #include <xen/softirq.h> @@ -749,17 +750,25 @@ static void p2m_free_entry(struct p2m_domain *p2m, if ( !p2m_is_valid(entry) ) return; - /* Nothing to do but updating the stats if the entry is a super-page. */ - if ( p2m_is_superpage(entry, level) ) + if ( p2m_is_superpage(entry, level) || (level == 3) ) { - p2m->stats.mappings[level]--; - return; - } +#ifdef CONFIG_IOREQ_SERVER + /* + * If this gets called then either the entry was replaced by an entry + * with a different base (valid case) or the shattering of a superpage + * has failed (error case). + * So, at worst, the spurious mapcache invalidation might be sent. + */ + if ( (p2m->domain == current->domain) && + domain_has_ioreq_server(p2m->domain) && + p2m_is_ram(entry.p2m.type) ) + p2m->domain->mapcache_invalidate = true; +#endif - if ( level == 3 ) - { p2m->stats.mappings[level]--; - p2m_put_l3_page(entry); + /* Nothing to do if the entry is a super-page. */ + if ( level == 3 ) + p2m_put_l3_page(entry); return; } diff --git a/xen/arch/arm/traps.c b/xen/arch/arm/traps.c index 476900e..6fa1350 100644 --- a/xen/arch/arm/traps.c +++ b/xen/arch/arm/traps.c @@ -1451,6 +1451,7 @@ static void do_trap_hypercall(struct cpu_user_regs *regs, register_t *nr, const union hsr hsr) { arm_hypercall_fn_t call = NULL; + struct vcpu *curr = current; BUILD_BUG_ON(NR_hypercalls < ARRAY_SIZE(arm_hypercall_table) ); @@ -1467,7 +1468,7 @@ static void do_trap_hypercall(struct cpu_user_regs *regs, register_t *nr, return; } - current->hcall_preempted = false; + curr->hcall_preempted = false; perfc_incra(hypercalls, *nr); call = arm_hypercall_table[*nr].fn; @@ -1480,7 +1481,7 @@ static void do_trap_hypercall(struct cpu_user_regs *regs, register_t *nr, HYPERCALL_RESULT_REG(regs) = call(HYPERCALL_ARGS(regs)); #ifndef NDEBUG - if ( !current->hcall_preempted ) + if ( !curr->hcall_preempted ) { /* Deliberately corrupt parameter regs used by this hypercall. */ switch ( arm_hypercall_table[*nr].nr_args ) { @@ -1497,8 +1498,21 @@ static void do_trap_hypercall(struct cpu_user_regs *regs, register_t *nr, #endif /* Ensure the hypercall trap instruction is re-executed. */ - if ( current->hcall_preempted ) + if ( curr->hcall_preempted ) regs->pc -= 4; /* re-execute 'hvc #XEN_HYPERCALL_TAG' */ + +#ifdef CONFIG_IOREQ_SERVER + /* + * We call ioreq_signal_mapcache_invalidate from do_trap_hypercall() + * because the only way a guest can modify its P2M on Arm is via an + * hypercall. + * Note that sending the invalidation request causes the vCPU to block + * until all the IOREQ servers have acknowledged the invalidation. + */ + if ( unlikely(curr->domain->mapcache_invalidate) && + test_and_clear_bool(curr->domain->mapcache_invalidate) ) + ioreq_signal_mapcache_invalidate(); +#endif } void arch_hypercall_tasklet_result(struct vcpu *v, long res) -- 2.7.4
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