[PATCH AUTOSEL 5.0 17/34] x86: kvm: hyper-v: deal with buggy TLB flush requests from WS2012

[PATCH AUTOSEL 5.0 17/34] x86: kvm: hyper-v: deal with buggy TLB flush requests from WS2012

[Sasha Levin]

From: Vitaly Kuznetsov <vkuznets@redhat.com>

[ Upstream commit da66761c2d93a46270d69001abb5692717495a68 ]

It was reported that with some special Multi Processor Group configuration,
e.g:
 bcdedit.exe /set groupsize 1
 bcdedit.exe /set maxgroup on
 bcdedit.exe /set groupaware on
for a 16-vCPU guest WS2012 shows BSOD on boot when PV TLB flush mechanism
is in use.

Tracing kvm_hv_flush_tlb immediately reveals the issue:

 kvm_hv_flush_tlb: processor_mask 0x0 address_space 0x0 flags 0x2

The only flag set in this request is HV_FLUSH_ALL_VIRTUAL_ADDRESS_SPACES,
however, processor_mask is 0x0 and no HV_FLUSH_ALL_PROCESSORS is specified.
We don't flush anything and apparently it's not what Windows expects.

TLFS doesn't say anything about such requests and newer Windows versions
seem to be unaffected. This all feels like a WS2012 bug, which is, however,
easy to workaround in KVM: let's flush everything when we see an empty
flush request, over-flushing doesn't hurt.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 arch/x86/kvm/hyperv.c | 11 ++++++++++-
 1 file changed, 10 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index 371c669696d70..610c0f1fbdd71 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -1371,7 +1371,16 @@ static u64 kvm_hv_flush_tlb(struct kvm_vcpu *current_vcpu, u64 ingpa,
 
 		valid_bank_mask = BIT_ULL(0);
 		sparse_banks[0] = flush.processor_mask;
-		all_cpus = flush.flags & HV_FLUSH_ALL_PROCESSORS;
+
+		/*
+		 * Work around possible WS2012 bug: it sends hypercalls
+		 * with processor_mask = 0x0 and HV_FLUSH_ALL_PROCESSORS clear,
+		 * while also expecting us to flush something and crashing if
+		 * we don't. Let's treat processor_mask == 0 same as
+		 * HV_FLUSH_ALL_PROCESSORS.
+		 */
+		all_cpus = (flush.flags & HV_FLUSH_ALL_PROCESSORS) ||
+			flush.processor_mask == 0;
 	} else {
 		if (unlikely(kvm_read_guest(kvm, ingpa, &flush_ex,
 					    sizeof(flush_ex))))
-- 
2.20.1

[PATCH AUTOSEL 5.0 28/34] KVM: fix KVM_CLEAR_DIRTY_LOG for memory slots of unaligned size

[Sasha Levin]

From: Paolo Bonzini <pbonzini@redhat.com>

[ Upstream commit 76d58e0f07ec203bbdfcaabd9a9fc10a5a3ed5ea ]

If a memory slot's size is not a multiple of 64 pages (256K), then
the KVM_CLEAR_DIRTY_LOG API is unusable: clearing the final 64 pages
either requires the requested page range to go beyond memslot->npages,
or requires log->num_pages to be unaligned, and kvm_clear_dirty_log_protect
requires log->num_pages to be both in range and aligned.

To allow this case, allow log->num_pages not to be a multiple of 64 if
it ends exactly on the last page of the slot.

Reported-by: Peter Xu <peterx@redhat.com>
Fixes: 98938aa8edd6 ("KVM: validate userspace input in kvm_clear_dirty_log_protect()", 2019-01-02)
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 Documentation/virtual/kvm/api.txt            | 5 +++--
 tools/testing/selftests/kvm/dirty_log_test.c | 9 ++++++---
 virt/kvm/kvm_main.c                          | 7 ++++---
 3 files changed, 13 insertions(+), 8 deletions(-)

diff --git a/Documentation/virtual/kvm/api.txt b/Documentation/virtual/kvm/api.txt
index ba8927c0d45c4..a1b8e6d92298c 100644
--- a/Documentation/virtual/kvm/api.txt
+++ b/Documentation/virtual/kvm/api.txt
@@ -3790,8 +3790,9 @@ The ioctl clears the dirty status of pages in a memory slot, according to
 the bitmap that is passed in struct kvm_clear_dirty_log's dirty_bitmap
 field.  Bit 0 of the bitmap corresponds to page "first_page" in the
 memory slot, and num_pages is the size in bits of the input bitmap.
-Both first_page and num_pages must be a multiple of 64.  For each bit
-that is set in the input bitmap, the corresponding page is marked "clean"
+first_page must be a multiple of 64; num_pages must also be a multiple of
+64 unless first_page + num_pages is the size of the memory slot.  For each
+bit that is set in the input bitmap, the corresponding page is marked "clean"
 in KVM's dirty bitmap, and dirty tracking is re-enabled for that page
 (for example via write-protection, or by clearing the dirty bit in
 a page table entry).
diff --git a/tools/testing/selftests/kvm/dirty_log_test.c b/tools/testing/selftests/kvm/dirty_log_test.c
index 4715cfba20dce..93f99c6b7d79e 100644
--- a/tools/testing/selftests/kvm/dirty_log_test.c
+++ b/tools/testing/selftests/kvm/dirty_log_test.c
@@ -288,8 +288,11 @@ static void run_test(enum vm_guest_mode mode, unsigned long iterations,
 #endif
 	max_gfn = (1ul << (guest_pa_bits - guest_page_shift)) - 1;
 	guest_page_size = (1ul << guest_page_shift);
-	/* 1G of guest page sized pages */
-	guest_num_pages = (1ul << (30 - guest_page_shift));
+	/*
+	 * A little more than 1G of guest page sized pages.  Cover the
+	 * case where the size is not aligned to 64 pages.
+	 */
+	guest_num_pages = (1ul << (30 - guest_page_shift)) + 3;
 	host_page_size = getpagesize();
 	host_num_pages = (guest_num_pages * guest_page_size) / host_page_size +
 			 !!((guest_num_pages * guest_page_size) % host_page_size);
@@ -359,7 +362,7 @@ static void run_test(enum vm_guest_mode mode, unsigned long iterations,
 		kvm_vm_get_dirty_log(vm, TEST_MEM_SLOT_INDEX, bmap);
 #ifdef USE_CLEAR_DIRTY_LOG
 		kvm_vm_clear_dirty_log(vm, TEST_MEM_SLOT_INDEX, bmap, 0,
-				       DIV_ROUND_UP(host_num_pages, 64) * 64);
+				       host_num_pages);
 #endif
 		vm_dirty_log_verify(bmap);
 		iteration++;
diff --git a/virt/kvm/kvm_main.c b/virt/kvm/kvm_main.c
index b4f2d892a1d36..c9b102e65a3a7 100644
--- a/virt/kvm/kvm_main.c
+++ b/virt/kvm/kvm_main.c
@@ -1241,7 +1241,7 @@ int kvm_clear_dirty_log_protect(struct kvm *kvm,
 	if (as_id >= KVM_ADDRESS_SPACE_NUM || id >= KVM_USER_MEM_SLOTS)
 		return -EINVAL;
 
-	if ((log->first_page & 63) || (log->num_pages & 63))
+	if (log->first_page & 63)
 		return -EINVAL;
 
 	slots = __kvm_memslots(kvm, as_id);
@@ -1254,8 +1254,9 @@ int kvm_clear_dirty_log_protect(struct kvm *kvm,
 	n = kvm_dirty_bitmap_bytes(memslot);
 
 	if (log->first_page > memslot->npages ||
-	    log->num_pages > memslot->npages - log->first_page)
-			return -EINVAL;
+	    log->num_pages > memslot->npages - log->first_page ||
+	    (log->num_pages < memslot->npages - log->first_page && (log->num_pages & 63)))
+	    return -EINVAL;
 
 	*flush = false;
 	dirty_bitmap_buffer = kvm_second_dirty_bitmap(memslot);
-- 
2.20.1

[PATCH AUTOSEL 5.0 29/34] KVM: selftests: make hyperv_cpuid test pass on AMD

[Sasha Levin]

From: Vitaly Kuznetsov <vkuznets@redhat.com>

[ Upstream commit eba3afde1cea7dbd7881683232f2a85e2ed86bfe ]

Enlightened VMCS is only supported on Intel CPUs but the test shouldn't
fail completely.

Signed-off-by: Vitaly Kuznetsov <vkuznets@redhat.com>
Signed-off-by: Paolo Bonzini <pbonzini@redhat.com>
Signed-off-by: Sasha Levin <sashal@kernel.org>
---
 tools/testing/selftests/kvm/x86_64/hyperv_cpuid.c | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/tools/testing/selftests/kvm/x86_64/hyperv_cpuid.c b/tools/testing/selftests/kvm/x86_64/hyperv_cpuid.c
index 264425f75806b..9a21e912097c4 100644
--- a/tools/testing/selftests/kvm/x86_64/hyperv_cpuid.c
+++ b/tools/testing/selftests/kvm/x86_64/hyperv_cpuid.c
@@ -141,7 +141,13 @@ int main(int argc, char *argv[])
 
 	free(hv_cpuid_entries);
 
-	vcpu_ioctl(vm, VCPU_ID, KVM_ENABLE_CAP, &enable_evmcs_cap);
+	rv = _vcpu_ioctl(vm, VCPU_ID, KVM_ENABLE_CAP, &enable_evmcs_cap);
+
+	if (rv) {
+		fprintf(stderr,
+			"Enlightened VMCS is unsupported, skip related test\n");
+		goto vm_free;
+	}
 
 	hv_cpuid_entries = kvm_get_supported_hv_cpuid(vm);
 	if (!hv_cpuid_entries)
@@ -151,6 +157,7 @@ int main(int argc, char *argv[])
 
 	free(hv_cpuid_entries);
 
+vm_free:
 	kvm_vm_free(vm);
 
 	return 0;
-- 
2.20.1