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KVM: Use NULL for struct page pointer to indicate mremapped memory

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Drop yet another unnecessary magic page value from KVM, as there's zero
reason to use a poisoned pointer to indicate "no page".  If KVM uses a
NULL page pointer, the kernel will explode just as quickly as if KVM uses
a poisoned pointer.  Never mind the fact that such usage would be a
blatant and egregious KVM bug.

Tested-by: Alex Bennée <alex.bennee@linaro.org>
Signed-off-by: Sean Christopherson <seanjc@google.com>
Tested-by: Dmitry Osipenko <dmitry.osipenko@collabora.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Message-ID: <20241010182427.1434605-23-seanjc@google.com>
This commit is contained in:
Sean Christopherson 2024-10-10 11:23:24 -07:00 committed by Paolo Bonzini
parent 5488499f9c
commit ef7db98e47
2 changed files with 2 additions and 6 deletions
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4
include/linux/kvm_host.h
View File

@ -273,16 +273,12 @@ enum {
READING_SHADOW_PAGE_TABLES,
};
#define KVM_UNMAPPED_PAGE ((void *) 0x500 + POISON_POINTER_DELTA)
struct kvm_host_map {
/*
* Only valid if the 'pfn' is managed by the host kernel (i.e. There is
* a 'struct page' for it. When using mem= kernel parameter some memory
* can be used as guest memory but they are not managed by host
* kernel).
* If 'pfn' is not managed by the host kernel, this field is
* initialized to KVM_UNMAPPED_PAGE.
*/
struct page *page;
void *hva;

4
virt/kvm/kvm_main.c
View File

@ -3061,7 +3061,7 @@ void kvm_release_pfn(kvm_pfn_t pfn, bool dirty)
int kvm_vcpu_map(struct kvm_vcpu *vcpu, gfn_t gfn, struct kvm_host_map *map)
{
map->page = KVM_UNMAPPED_PAGE;
map->page = NULL;
map->hva = NULL;
map->gfn = gfn;
@ -3087,7 +3087,7 @@ void kvm_vcpu_unmap(struct kvm_vcpu *vcpu, struct kvm_host_map *map, bool dirty)
if (!map->hva)
return;
if (map->page != KVM_UNMAPPED_PAGE)
if (map->page)
kunmap(map->page);
#ifdef CONFIG_HAS_IOMEM
else