Commit 58f5ee5f authored by Sean Christopherson's avatar Sean Christopherson Committed by David Woodhouse
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KVM: Drop @gpa from exported gfn=>pfn cache check() and refresh() helpers 



Drop the @gpa param from the exported check()+refresh() helpers and limit
changing the cache's GPA to the activate path.  All external users just
feed in gpc->gpa, i.e. this is a fancy nop.

Allowing users to change the GPA at check()+refresh() is dangerous as
those helpers explicitly allow concurrent calls, e.g. KVM could get into
a livelock scenario.  It's also unclear as to what the expected behavior
should be if multiple tasks attempt to refresh with different GPAs.

Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
Signed-off-by: default avatarDavid Woodhouse <dwmw@amazon.co.uk>
parent 5762cb10

arch/x86/kvm/x86.c

+2 −4
Original line number Diff line number Diff line
@@ -3035,12 +3035,10 @@ static void kvm_setup_guest_pvclock(struct kvm_vcpu *v, 
	unsigned long flags;



	read_lock_irqsave(&gpc->lock, flags);

	while (!kvm_gpc_check(gpc, gpc->gpa,

			      offset + sizeof(*guest_hv_clock))) {

	while (!kvm_gpc_check(gpc, offset + sizeof(*guest_hv_clock))) {

		read_unlock_irqrestore(&gpc->lock, flags);



		if (kvm_gpc_refresh(gpc, gpc->gpa,

				    offset + sizeof(*guest_hv_clock)))

		if (kvm_gpc_refresh(gpc, offset + sizeof(*guest_hv_clock)))

			return;



		read_lock_irqsave(&gpc->lock, flags);

arch/x86/kvm/xen.c

+11 −11
Original line number Diff line number Diff line
@@ -272,14 +272,14 @@ static void kvm_xen_update_runstate_guest(struct kvm_vcpu *v, bool atomic) 
	 * gfn_to_pfn caches that cover the region.

	 */

	read_lock_irqsave(&gpc1->lock, flags);

	while (!kvm_gpc_check(gpc1, gpc1->gpa, user_len1)) {

	while (!kvm_gpc_check(gpc1, user_len1)) {

		read_unlock_irqrestore(&gpc1->lock, flags);



		/* When invoked from kvm_sched_out() we cannot sleep */

		if (atomic)

			return;



		if (kvm_gpc_refresh(gpc1, gpc1->gpa, user_len1))

		if (kvm_gpc_refresh(gpc1, user_len1))

			return;



		read_lock_irqsave(&gpc1->lock, flags);
@@ -308,7 +308,7 @@ static void kvm_xen_update_runstate_guest(struct kvm_vcpu *v, bool atomic) 
		 */

		read_lock(&gpc2->lock);



		if (!kvm_gpc_check(gpc2, gpc2->gpa, user_len2)) {

		if (!kvm_gpc_check(gpc2, user_len2)) {

			read_unlock(&gpc2->lock);

			read_unlock_irqrestore(&gpc1->lock, flags);
@@ -488,10 +488,10 @@ void kvm_xen_inject_pending_events(struct kvm_vcpu *v) 
	 * little more honest about it.

	 */

	read_lock_irqsave(&gpc->lock, flags);

	while (!kvm_gpc_check(gpc, gpc->gpa, sizeof(struct vcpu_info))) {

	while (!kvm_gpc_check(gpc, sizeof(struct vcpu_info))) {

		read_unlock_irqrestore(&gpc->lock, flags);



		if (kvm_gpc_refresh(gpc, gpc->gpa, sizeof(struct vcpu_info)))

		if (kvm_gpc_refresh(gpc, sizeof(struct vcpu_info)))

			return;



		read_lock_irqsave(&gpc->lock, flags);
@@ -551,7 +551,7 @@ int __kvm_xen_has_interrupt(struct kvm_vcpu *v) 
		     sizeof_field(struct compat_vcpu_info, evtchn_upcall_pending));



	read_lock_irqsave(&gpc->lock, flags);

	while (!kvm_gpc_check(gpc, gpc->gpa, sizeof(struct vcpu_info))) {

	while (!kvm_gpc_check(gpc, sizeof(struct vcpu_info))) {

		read_unlock_irqrestore(&gpc->lock, flags);



		/*
@@ -565,7 +565,7 @@ int __kvm_xen_has_interrupt(struct kvm_vcpu *v) 
		if (in_atomic() || !task_is_running(current))

			return 1;



		if (kvm_gpc_refresh(gpc, gpc->gpa, sizeof(struct vcpu_info))) {

		if (kvm_gpc_refresh(gpc, sizeof(struct vcpu_info))) {

			/*

			 * If this failed, userspace has screwed up the

			 * vcpu_info mapping. No interrupts for you.
@@ -1154,7 +1154,7 @@ static bool wait_pending_event(struct kvm_vcpu *vcpu, int nr_ports, 


	read_lock_irqsave(&gpc->lock, flags);

	idx = srcu_read_lock(&kvm->srcu);

	if (!kvm_gpc_check(gpc, gpc->gpa, PAGE_SIZE))

	if (!kvm_gpc_check(gpc, PAGE_SIZE))

		goto out_rcu;



	ret = false;
@@ -1576,7 +1576,7 @@ int kvm_xen_set_evtchn_fast(struct kvm_xen_evtchn *xe, struct kvm *kvm) 
	idx = srcu_read_lock(&kvm->srcu);



	read_lock_irqsave(&gpc->lock, flags);

	if (!kvm_gpc_check(gpc, gpc->gpa, PAGE_SIZE))

	if (!kvm_gpc_check(gpc, PAGE_SIZE))

		goto out_rcu;



	if (IS_ENABLED(CONFIG_64BIT) && kvm->arch.xen.long_mode) {
@@ -1610,7 +1610,7 @@ int kvm_xen_set_evtchn_fast(struct kvm_xen_evtchn *xe, struct kvm *kvm) 
		gpc = &vcpu->arch.xen.vcpu_info_cache;



		read_lock_irqsave(&gpc->lock, flags);

		if (!kvm_gpc_check(gpc, gpc->gpa, sizeof(struct vcpu_info))) {

		if (!kvm_gpc_check(gpc, sizeof(struct vcpu_info))) {

			/*

			 * Could not access the vcpu_info. Set the bit in-kernel

			 * and prod the vCPU to deliver it for itself.
@@ -1708,7 +1708,7 @@ static int kvm_xen_set_evtchn(struct kvm_xen_evtchn *xe, struct kvm *kvm) 
			break;



		idx = srcu_read_lock(&kvm->srcu);

		rc = kvm_gpc_refresh(gpc, gpc->gpa, PAGE_SIZE);

		rc = kvm_gpc_refresh(gpc, PAGE_SIZE);

		srcu_read_unlock(&kvm->srcu, idx);

	} while(!rc);

include/linux/kvm_host.h

+3 −5
Original line number Diff line number Diff line
@@ -1299,7 +1299,6 @@ int kvm_gpc_activate(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned long len) 
 * kvm_gpc_check - check validity of a gfn_to_pfn_cache.

 *

 * @gpc:	   struct gfn_to_pfn_cache object.

 * @gpa:	   current guest physical address to map.

 * @len:	   sanity check; the range being access must fit a single page.

 *

 * @return:	   %true if the cache is still valid and the address matches.
@@ -1312,15 +1311,14 @@ int kvm_gpc_activate(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned long len) 
 * Callers in IN_GUEST_MODE may do so without locking, although they should

 * still hold a read lock on kvm->scru for the memslot checks.

 */

bool kvm_gpc_check(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned long len);

bool kvm_gpc_check(struct gfn_to_pfn_cache *gpc, unsigned long len);



/**

 * kvm_gpc_refresh - update a previously initialized cache.

 *

 * @gpc:	   struct gfn_to_pfn_cache object.

 * @gpa:	   updated guest physical address to map.

 * @len:	   sanity check; the range being access must fit a single page.



 *

 * @return:	   0 for success.

 *		   -EINVAL for a mapping which would cross a page boundary.

 *		   -EFAULT for an untranslatable guest physical address.
@@ -1331,7 +1329,7 @@ bool kvm_gpc_check(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned long len); 
 * still lock and check the cache status, as this function does not return

 * with the lock still held to permit access.

 */

int kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned long len);

int kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, unsigned long len);



/**

 * kvm_gpc_deactivate - deactivate and unlink a gfn_to_pfn_cache.

virt/kvm/pfncache.c

+11 −6
Original line number Diff line number Diff line
@@ -76,18 +76,17 @@ void gfn_to_pfn_cache_invalidate_start(struct kvm *kvm, unsigned long start, 
	}

}



bool kvm_gpc_check(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned long len)

bool kvm_gpc_check(struct gfn_to_pfn_cache *gpc, unsigned long len)

{

	struct kvm_memslots *slots = kvm_memslots(gpc->kvm);



	if (!gpc->active)

		return false;



	if ((gpa & ~PAGE_MASK) + len > PAGE_SIZE)

	if ((gpc->gpa & ~PAGE_MASK) + len > PAGE_SIZE)

		return false;



	if (gpc->gpa != gpa || gpc->generation != slots->generation ||

	    kvm_is_error_hva(gpc->uhva))

	if (gpc->generation != slots->generation || kvm_is_error_hva(gpc->uhva))

		return false;



	if (!gpc->valid)
@@ -237,7 +236,8 @@ static kvm_pfn_t hva_to_pfn_retry(struct gfn_to_pfn_cache *gpc) 
	return -EFAULT;

}



int kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned long len)

static int __kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, gpa_t gpa,

			     unsigned long len)

{

	struct kvm_memslots *slots = kvm_memslots(gpc->kvm);

	unsigned long page_offset = gpa & ~PAGE_MASK;
@@ -331,6 +331,11 @@ int kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned long len) 


	return ret;

}



int kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, unsigned long len)

{

	return __kvm_gpc_refresh(gpc, gpc->gpa, len);

}

EXPORT_SYMBOL_GPL(kvm_gpc_refresh);



void kvm_gpc_init(struct gfn_to_pfn_cache *gpc, struct kvm *kvm,
@@ -371,7 +376,7 @@ int kvm_gpc_activate(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned long len) 
		gpc->active = true;

		write_unlock_irq(&gpc->lock);

	}

	return kvm_gpc_refresh(gpc, gpa, len);

	return __kvm_gpc_refresh(gpc, gpa, len);

}

EXPORT_SYMBOL_GPL(kvm_gpc_activate);