Commit 721f5b0d authored by Paul Durrant's avatar Paul Durrant Committed by Sean Christopherson
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KVM: pfncache: allow a cache to be activated with a fixed (userspace) HVA 



Some pfncache pages may actually be overlays on guest memory that have a
fixed HVA within the VMM. It's pointless to invalidate such cached
mappings if the overlay is moved so allow a cache to be activated directly
with the HVA to cater for such cases. A subsequent patch will make use
of this facility.

Signed-off-by: default avatarPaul Durrant <pdurrant@amazon.com>
Reviewed-by: default avatarDavid Woodhouse <dwmw@amazon.co.uk>
Link: https://lore.kernel.org/r/20240215152916.1158-10-paul@xen.org


Signed-off-by: default avatarSean Christopherson <seanjc@google.com>
parent 9e7325ac

include/linux/kvm_host.h

+31 −0
Original line number Diff line number Diff line
@@ -148,6 +148,11 @@ static inline bool kvm_is_error_hva(unsigned long addr) 


#endif



static inline bool kvm_is_error_gpa(gpa_t gpa)

{

	return gpa == INVALID_GPA;

}



#define KVM_ERR_PTR_BAD_PAGE	(ERR_PTR(-ENOENT))



static inline bool is_error_page(struct page *page)
@@ -1344,6 +1349,22 @@ void kvm_gpc_init(struct gfn_to_pfn_cache *gpc, struct kvm *kvm); 
 */

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



/**

 * kvm_gpc_activate_hva - prepare a cached kernel mapping and HPA for a given HVA.

 *

 * @gpc:          struct gfn_to_pfn_cache object.

 * @hva:          userspace virtual 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.

 *

 * The semantics of this function are the same as those of kvm_gpc_activate(). It

 * merely bypasses a layer of address translation.

 */

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



/**

 * kvm_gpc_check - check validity of a gfn_to_pfn_cache.

 *
@@ -1390,6 +1411,16 @@ int kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, unsigned long len); 
 */

void kvm_gpc_deactivate(struct gfn_to_pfn_cache *gpc);



static inline bool kvm_gpc_is_gpa_active(struct gfn_to_pfn_cache *gpc)

{

	return gpc->active && !kvm_is_error_gpa(gpc->gpa);

}



static inline bool kvm_gpc_is_hva_active(struct gfn_to_pfn_cache *gpc)

{

	return gpc->active && kvm_is_error_gpa(gpc->gpa);

}



void kvm_sigset_activate(struct kvm_vcpu *vcpu);

void kvm_sigset_deactivate(struct kvm_vcpu *vcpu);

virt/kvm/pfncache.c

+70 −28
Original line number Diff line number Diff line
@@ -48,7 +48,14 @@ bool kvm_gpc_check(struct gfn_to_pfn_cache *gpc, unsigned long len) 
	if (!gpc->active)

		return false;



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

	/*

	 * If the page was cached from a memslot, make sure the memslots have

	 * not been re-configured.

	 */

	if (!kvm_is_error_gpa(gpc->gpa) && gpc->generation != slots->generation)

		return false;



	if (kvm_is_error_hva(gpc->uhva))

		return false;



	if (offset_in_page(gpc->uhva) + len > PAGE_SIZE)
@@ -209,11 +216,10 @@ static kvm_pfn_t hva_to_pfn_retry(struct gfn_to_pfn_cache *gpc) 
	return -EFAULT;

}



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

static int __kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned long uhva,

			     unsigned long len)

{

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

	unsigned long page_offset = offset_in_page(gpa);

	unsigned long page_offset;

	bool unmap_old = false;

	unsigned long old_uhva;

	kvm_pfn_t old_pfn;
@@ -221,10 +227,16 @@ static int __kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, gpa_t gpa, 
	void *old_khva;

	int ret;



	/* Either gpa or uhva must be valid, but not both */

	if (WARN_ON_ONCE(kvm_is_error_gpa(gpa) == kvm_is_error_hva(uhva)))

		return -EINVAL;



	/*

	 * If must fit within a single page. The 'len' argument is

	 * only to enforce that.

	 * The cached acces must fit within a single page. The 'len' argument

	 * exists only to enforce that.

	 */

	page_offset = kvm_is_error_gpa(gpa) ? offset_in_page(uhva) :

					      offset_in_page(gpa);

	if (page_offset + len > PAGE_SIZE)

		return -EINVAL;
@@ -246,7 +258,16 @@ static int __kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, gpa_t gpa, 
	old_khva = (void *)PAGE_ALIGN_DOWN((uintptr_t)gpc->khva);

	old_uhva = PAGE_ALIGN_DOWN(gpc->uhva);



	/* Refresh the userspace HVA if necessary */

	if (kvm_is_error_gpa(gpa)) {

		gpc->gpa = INVALID_GPA;

		gpc->memslot = NULL;

		gpc->uhva = PAGE_ALIGN_DOWN(uhva);



		if (gpc->uhva != old_uhva)

			hva_change = true;

	} else {

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



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

		    kvm_is_error_hva(gpc->uhva)) {

			gfn_t gfn = gpa_to_gfn(gpa);
@@ -270,6 +291,7 @@ static int __kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, gpa_t gpa, 
		} else {

			gpc->uhva = old_uhva;

		}

	}



	/* Note: the offset must be correct before calling hva_to_pfn_retry() */

	gpc->uhva += page_offset;
@@ -319,7 +341,15 @@ static int __kvm_gpc_refresh(struct gfn_to_pfn_cache *gpc, gpa_t gpa, 


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

{

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

	/*

	 * If the GPA is valid then ignore the HVA, as a cache can be GPA-based

	 * or HVA-based, not both.  For GPA-based caches, the HVA will be

	 * recomputed during refresh if necessary.

	 */

	unsigned long uhva = kvm_is_error_gpa(gpc->gpa) ? gpc->uhva :

							  KVM_HVA_ERR_BAD;



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

}



void kvm_gpc_init(struct gfn_to_pfn_cache *gpc, struct kvm *kvm)
@@ -329,10 +359,12 @@ void kvm_gpc_init(struct gfn_to_pfn_cache *gpc, struct kvm *kvm) 


	gpc->kvm = kvm;

	gpc->pfn = KVM_PFN_ERR_FAULT;

	gpc->gpa = INVALID_GPA;

	gpc->uhva = KVM_HVA_ERR_BAD;

}



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

static int __kvm_gpc_activate(struct gfn_to_pfn_cache *gpc, gpa_t gpa, unsigned long uhva,

			      unsigned long len)

{

	struct kvm *kvm = gpc->kvm;
@@ -353,7 +385,17 @@ 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, uhva, len);

}



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

{

	return __kvm_gpc_activate(gpc, gpa, KVM_HVA_ERR_BAD, len);

}



int kvm_gpc_activate_hva(struct gfn_to_pfn_cache *gpc, unsigned long uhva, unsigned long len)

{

	return __kvm_gpc_activate(gpc, INVALID_GPA, uhva, len);

}



void kvm_gpc_deactivate(struct gfn_to_pfn_cache *gpc)