diff options
| author | Sean Christopherson <seanjc@google.com> | 2024-10-10 20:24:18 +0200 |
|---|---|---|
| committer | Paolo Bonzini <pbonzini@redhat.com> | 2024-10-25 19:00:50 +0200 |
| commit | f42e289a2095f61755e6ca5fd1370d441bf589d5 (patch) | |
| tree | fce15b66ea8ee18be28f3e409a1748bdcd20c5c2 | |
| parent | KVM: Convert gfn_to_page() to use kvm_follow_pfn() (diff) | |
| download | linux-f42e289a2095f61755e6ca5fd1370d441bf589d5.tar.xz linux-f42e289a2095f61755e6ca5fd1370d441bf589d5.zip | |
KVM: Add support for read-only usage of gfn_to_page()
Rework gfn_to_page() to support read-only accesses so that it can be used
by arm64 to get MTE tags out of guest memory.
Opportunistically rewrite the comment to be even more stern about using
gfn_to_page(), as there are very few scenarios where requiring a struct
page is actually the right thing to do (though there are such scenarios).
Add a FIXME to call out that KVM probably should be pinning pages, not
just getting pages.
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: <20241010182427.1434605-77-seanjc@google.com>
| -rw-r--r-- | include/linux/kvm_host.h | 7 | ||||
| -rw-r--r-- | virt/kvm/kvm_main.c | 15 |
2 files changed, 14 insertions, 8 deletions
diff --git a/include/linux/kvm_host.h b/include/linux/kvm_host.h index 3e06393e5f1e..96cf9e5660c3 100644 --- a/include/linux/kvm_host.h +++ b/include/linux/kvm_host.h @@ -1213,7 +1213,12 @@ void kvm_arch_flush_shadow_memslot(struct kvm *kvm, int kvm_prefetch_pages(struct kvm_memory_slot *slot, gfn_t gfn, struct page **pages, int nr_pages); -struct page *gfn_to_page(struct kvm *kvm, gfn_t gfn); +struct page *__gfn_to_page(struct kvm *kvm, gfn_t gfn, bool write); +static inline struct page *gfn_to_page(struct kvm *kvm, gfn_t gfn) +{ + return __gfn_to_page(kvm, gfn, true); +} + unsigned long gfn_to_hva(struct kvm *kvm, gfn_t gfn); unsigned long gfn_to_hva_prot(struct kvm *kvm, gfn_t gfn, bool *writable); unsigned long gfn_to_hva_memslot(struct kvm_memory_slot *slot, gfn_t gfn); diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c index 5a424598610f..1c11a05a97af 100644 --- a/virt/kvm/kvm_main.c +++ b/virt/kvm/kvm_main.c @@ -3132,25 +3132,26 @@ int kvm_prefetch_pages(struct kvm_memory_slot *slot, gfn_t gfn, EXPORT_SYMBOL_GPL(kvm_prefetch_pages); /* - * Do not use this helper unless you are absolutely certain the gfn _must_ be - * backed by 'struct page'. A valid example is if the backing memslot is - * controlled by KVM. Note, if the returned page is valid, it's refcount has - * been elevated by gfn_to_pfn(). + * Don't use this API unless you are absolutely, positively certain that KVM + * needs to get a struct page, e.g. to pin the page for firmware DMA. + * + * FIXME: Users of this API likely need to FOLL_PIN the page, not just elevate + * its refcount. */ -struct page *gfn_to_page(struct kvm *kvm, gfn_t gfn) +struct page *__gfn_to_page(struct kvm *kvm, gfn_t gfn, bool write) { struct page *refcounted_page = NULL; struct kvm_follow_pfn kfp = { .slot = gfn_to_memslot(kvm, gfn), .gfn = gfn, - .flags = FOLL_WRITE, + .flags = write ? FOLL_WRITE : 0, .refcounted_page = &refcounted_page, }; (void)kvm_follow_pfn(&kfp); return refcounted_page; } -EXPORT_SYMBOL_GPL(gfn_to_page); +EXPORT_SYMBOL_GPL(__gfn_to_page); int __kvm_vcpu_map(struct kvm_vcpu *vcpu, gfn_t gfn, struct kvm_host_map *map, bool writable) |