Re: [PATCH 03/13] x86/HV: Add new hvcall guest address host visibility support
From: Dave Hansen <hidden>
Date: 2021-07-28 17:07:22
Also in:
linux-hyperv, linux-iommu, linux-scsi, lkml, netdev, xen-devel
On 7/28/21 7:52 AM, Tianyu Lan wrote:
quoted hunk ↗ jump to hunk
@@ -1986,7 +1988,9 @@ static int __set_memory_enc_dec(unsigned long addr, int numpages, bool enc) int ret; /* Nothing to do if memory encryption is not active */ - if (!mem_encrypt_active()) + if (hv_is_isolation_supported()) + return hv_set_mem_enc(addr, numpages, enc); + else if (!mem_encrypt_active()) return 0;
One more thing. If you're going to be patching generic code, please
start using feature checks that can get optimized away at runtime.
hv_is_isolation_supported() doesn't look like the world's cheapest
check. It can't be inlined and costs at least a function call.
These checks could, with basically no effort be wrapped in a header like
this:
static inline bool hv_is_isolation_supported(void)
{
if (!cpu_feature_enabled(X86_FEATURE_HYPERVISOR))
return 0;
// out of line function call:
return __hv_is_isolation_supported();
}
I don't think it would be the end of the world to add an
X86_FEATURE_HYPERV_GUEST, either. There are plenty of bits allocated
for Xen and VMWare.