From 999ad14259a0d45cb3b616e2e95a7c8b622a7ecd Mon Sep 17 00:00:00 2001 From: Michael Kelley Date: Tue, 18 Mar 2025 14:49:19 -0700 Subject: x86/hyperv: Add comments about hv_vpset and var size hypercall input args Current code varies in how the size of the variable size input header for hypercalls is calculated when the input contains struct hv_vpset. Surprisingly, this variation is correct, as different hypercalls make different choices for what portion of struct hv_vpset is treated as part of the variable size input header. The Hyper-V TLFS is silent on these details, but the behavior has been confirmed with Hyper-V developers. To avoid future confusion about these differences, add comments to struct hv_vpset, and to hypercall call sites with input that contains a struct hv_vpset. The comments describe the overall situation and the calculation that should be used at each particular call site. No functional change as only comments are updated. Signed-off-by: Michael Kelley Link: https://lore.kernel.org/r/20250318214919.958953-1-mhklinux@outlook.com Signed-off-by: Wei Liu Message-ID: <20250318214919.958953-1-mhklinux@outlook.com> --- arch/x86/hyperv/mmu.c | 4 ++++ 1 file changed, 4 insertions(+) (limited to 'arch/x86/hyperv/mmu.c') diff --git a/arch/x86/hyperv/mmu.c b/arch/x86/hyperv/mmu.c index cc8c3bd0e7c2..80d9350612d2 100644 --- a/arch/x86/hyperv/mmu.c +++ b/arch/x86/hyperv/mmu.c @@ -205,6 +205,10 @@ static u64 hyperv_flush_tlb_others_ex(const struct cpumask *cpus, /* * We can flush not more than max_gvas with one hypercall. Flush the * whole address space if we were asked to do more. + * + * For these hypercalls, Hyper-V treats the valid_bank_mask field + * of flush->hv_vp_set as part of the fixed size input header. + * So the variable input header size is equal to nr_bank. */ max_gvas = (PAGE_SIZE - sizeof(*flush) - nr_bank * -- cgit v1.2.3