2022-02-22 17:08:15

by Vitaly Kuznetsov

Subject: [PATCH 3/4] KVM: x86: hyper-v: Fix the maximum number of sparse banks for XMM fast TLB flush hypercalls

When TLB flush hypercalls (HVCALL_FLUSH_VIRTUAL_ADDRESS_{LIST,SPACE}_EX are
issued in 'XMM fast' mode, the maximum number of allowed sparse_banks is
not 'HV_HYPERCALL_MAX_XMM_REGISTERS - 1' (5) but twice as many (10) as each
XMM register is 128 bit long and can hold two 64 bit long banks.

Fixes: 5974565bc26d ("KVM: x86: kvm_hv_flush_tlb use inputs from XMM registers")
Signed-off-by: Vitaly Kuznetsov <[email protected]>
---
arch/x86/kvm/hyperv.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/arch/x86/kvm/hyperv.c b/arch/x86/kvm/hyperv.c
index 714af3b94f31..6dda93bf98ae 100644
--- a/arch/x86/kvm/hyperv.c
+++ b/arch/x86/kvm/hyperv.c
@@ -1820,7 +1820,8 @@ static u64 kvm_hv_flush_tlb(struct kvm_vcpu *vcpu, struct kvm_hv_hcall *hc)

if (!all_cpus) {
if (hc->fast) {
- if (sparse_banks_len > HV_HYPERCALL_MAX_XMM_REGISTERS - 1)
+ /* XMM0 is already consumed, each XMM holds two sparse banks. */
+ if (sparse_banks_len > 2 * (HV_HYPERCALL_MAX_XMM_REGISTERS - 1))
return HV_STATUS_INVALID_HYPERCALL_INPUT;
for (i = 0; i < sparse_banks_len; i += 2) {
sparse_banks[i] = sse128_lo(hc->xmm[i / 2 + 1]);
--
2.35.1

2022-02-28 13:24:13

by Siddharth Chandrasekaran

Subject: Re: [PATCH 3/4] KVM: x86: hyper-v: Fix the maximum number of sparse banks for XMM fast TLB flush hypercalls

On Tue, Feb 22, 2022 at 04:46:41PM +0100, Vitaly Kuznetsov wrote:
> CAUTION: This email originated from outside of the organization. Do not click links or open attachments unless you can confirm the sender and know the content is safe.
>
>
>
> When TLB flush hypercalls (HVCALL_FLUSH_VIRTUAL_ADDRESS_{LIST,SPACE}_EX are
> issued in 'XMM fast' mode, the maximum number of allowed sparse_banks is
> not 'HV_HYPERCALL_MAX_XMM_REGISTERS - 1' (5) but twice as many (10) as each
> XMM register is 128 bit long and can hold two 64 bit long banks.
>
> Fixes: 5974565bc26d ("KVM: x86: kvm_hv_flush_tlb use inputs from XMM registers")
> Signed-off-by: Vitaly Kuznetsov <[email protected]>

Indeed :)

Reviewed-by: Siddharth Chandrasekaran <[email protected]>



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