Commit d0d96121 authored by Sean Christopherson's avatar Sean Christopherson Committed by Paolo Bonzini
Browse files

KVM: Use enum to track if cached PFN will be used in guest and/or host 



Replace the guest_uses_pa and kernel_map booleans in the PFN cache code
with a unified enum/bitmask. Using explicit names makes it easier to
review and audit call sites.

Opportunistically add a WARN to prevent passing garbage; instantating a
cache without declaring its usage is either buggy or pointless.

Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
Signed-off-by: default avatarDavid Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
Message-Id: <20220303154127.202856-2-dwmw2@infradead.org>
Signed-off-by: default avatarPaolo Bonzini <pbonzini@redhat.com>
parent 4a9e7b9e

arch/x86/kvm/xen.c

+1 −1
Original line number Diff line number Diff line
@@ -39,7 +39,7 @@ static int kvm_xen_shared_info_init(struct kvm *kvm, gfn_t gfn) 
	}



	do {

		ret = kvm_gfn_to_pfn_cache_init(kvm, gpc, NULL, false, true,

		ret = kvm_gfn_to_pfn_cache_init(kvm, gpc, NULL, KVM_HOST_USES_PFN,

						gpa, PAGE_SIZE, false);

		if (ret)

			goto out;

include/linux/kvm_host.h

+8 −8
Original line number Diff line number Diff line
@@ -1231,11 +1231,12 @@ void kvm_vcpu_mark_page_dirty(struct kvm_vcpu *vcpu, gfn_t gfn); 
 * @gpc:	   struct gfn_to_pfn_cache object.

 * @vcpu:	   vCPU to be used for marking pages dirty and to be woken on

 *		   invalidation.

 * @guest_uses_pa: indicates that the resulting host physical PFN is used while

 *		   @vcpu is IN_GUEST_MODE; invalidations of the cache from MMU

 *		   notifiers (but not for KVM memslot changes!) will also force

 *		   @vcpu to exit the guest to refresh the cache.

 * @kernel_map:    requests a kernel virtual mapping (kmap / memremap).

 * @usage:	   indicates if the resulting host physical PFN is used while

 *		   the @vcpu is IN_GUEST_MODE (in which case invalidation of 

 *		   the cache from MMU notifiers---but not for KVM memslot

 *		   changes!---will also force @vcpu to exit the guest and

 *		   refresh the cache); and/or if the PFN used directly

 *		   by KVM (and thus needs a kernel virtual mapping).

 * @gpa:	   guest physical address to map.

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

 * @dirty:         mark the cache dirty immediately.
@@ -1250,9 +1251,8 @@ void kvm_vcpu_mark_page_dirty(struct kvm_vcpu *vcpu, gfn_t gfn); 
 * accessing the target page.

 */

int kvm_gfn_to_pfn_cache_init(struct kvm *kvm, struct gfn_to_pfn_cache *gpc,

			      struct kvm_vcpu *vcpu, bool guest_uses_pa,

			      bool kernel_map, gpa_t gpa, unsigned long len,

			      bool dirty);

			      struct kvm_vcpu *vcpu, enum pfn_cache_usage usage,

			      gpa_t gpa, unsigned long len, bool dirty);



/**

 * kvm_gfn_to_pfn_cache_check - check validity of a gfn_to_pfn_cache.

include/linux/kvm_types.h

+8 −2
Original line number Diff line number Diff line
@@ -18,6 +18,7 @@ struct kvm_memslots; 


enum kvm_mr_change;



#include <linux/bits.h>

#include <linux/types.h>

#include <linux/spinlock_types.h>
@@ -46,6 +47,12 @@ typedef u64 hfn_t; 


typedef hfn_t kvm_pfn_t;



enum pfn_cache_usage {

	KVM_GUEST_USES_PFN = BIT(0),

	KVM_HOST_USES_PFN  = BIT(1),

	KVM_GUEST_AND_HOST_USE_PFN = KVM_GUEST_USES_PFN | KVM_HOST_USES_PFN,

};



struct gfn_to_hva_cache {

	u64 generation;

	gpa_t gpa;
@@ -64,11 +71,10 @@ struct gfn_to_pfn_cache { 
	rwlock_t lock;

	void *khva;

	kvm_pfn_t pfn;

	enum pfn_cache_usage usage;

	bool active;

	bool valid;

	bool dirty;

	bool kernel_map;

	bool guest_uses_pa;

};



#ifdef KVM_ARCH_NR_OBJS_PER_MEMORY_CACHE

virt/kvm/pfncache.c

+7 −7
Original line number Diff line number Diff line
@@ -42,7 +42,7 @@ void gfn_to_pfn_cache_invalidate_start(struct kvm *kvm, unsigned long start, 
			 * If a guest vCPU could be using the physical address,

			 * it needs to be forced out of guest mode.

			 */

			if (gpc->guest_uses_pa) {

			if (gpc->usage & KVM_GUEST_USES_PFN) {

				if (!evict_vcpus) {

					evict_vcpus = true;

					bitmap_zero(vcpu_bitmap, KVM_MAX_VCPUS);
@@ -224,7 +224,7 @@ int kvm_gfn_to_pfn_cache_refresh(struct kvm *kvm, struct gfn_to_pfn_cache *gpc, 
			goto map_done;

		}



		if (gpc->kernel_map) {

		if (gpc->usage & KVM_HOST_USES_PFN) {

			if (new_pfn == old_pfn) {

				new_khva = old_khva;

				old_pfn = KVM_PFN_ERR_FAULT;
@@ -304,10 +304,11 @@ EXPORT_SYMBOL_GPL(kvm_gfn_to_pfn_cache_unmap); 




int kvm_gfn_to_pfn_cache_init(struct kvm *kvm, struct gfn_to_pfn_cache *gpc,

			      struct kvm_vcpu *vcpu, bool guest_uses_pa,

			      bool kernel_map, gpa_t gpa, unsigned long len,

			      bool dirty)

			      struct kvm_vcpu *vcpu, enum pfn_cache_usage usage,

			      gpa_t gpa, unsigned long len, bool dirty)

{

	WARN_ON_ONCE(!usage || (usage & KVM_GUEST_AND_HOST_USE_PFN) != usage);



	if (!gpc->active) {

		rwlock_init(&gpc->lock);
@@ -315,8 +316,7 @@ int kvm_gfn_to_pfn_cache_init(struct kvm *kvm, struct gfn_to_pfn_cache *gpc, 
		gpc->pfn = KVM_PFN_ERR_FAULT;

		gpc->uhva = KVM_HVA_ERR_BAD;

		gpc->vcpu = vcpu;

		gpc->kernel_map = kernel_map;

		gpc->guest_uses_pa = guest_uses_pa;

		gpc->usage = usage;

		gpc->valid = false;

		gpc->active = true;