On 6/9/2021 8:46 PM, Joerg Roedel wrote:
On Sun, May 30, 2021 at 11:06:21AM -0400, Tianyu Lan wrote:+void hv_ghcb_msr_write(u64 msr, u64 value) +{ + union hv_ghcb *hv_ghcb; + void **ghcb_base; + unsigned long flags; + + if (!ms_hyperv.ghcb_base) + return; + + local_irq_save(flags); + ghcb_base = (void **)this_cpu_ptr(ms_hyperv.ghcb_base); + hv_ghcb = (union hv_ghcb *)*ghcb_base; + if (!hv_ghcb) { + local_irq_restore(flags); + return; + } + + memset(hv_ghcb, 0x00, HV_HYP_PAGE_SIZE); + + hv_ghcb->ghcb.protocol_version = 1; + hv_ghcb->ghcb.ghcb_usage = 0; + + ghcb_set_sw_exit_code(&hv_ghcb->ghcb, SVM_EXIT_MSR); + ghcb_set_rcx(&hv_ghcb->ghcb, msr); + ghcb_set_rax(&hv_ghcb->ghcb, lower_32_bits(value)); + ghcb_set_rdx(&hv_ghcb->ghcb, value >> 32); + ghcb_set_sw_exit_info_1(&hv_ghcb->ghcb, 1); + ghcb_set_sw_exit_info_2(&hv_ghcb->ghcb, 0); + + VMGEXIT();This is not safe to use from NMI context. You need at least some checking or WARN_ON/assertion/whatever to catch cases where this is violated. Otherwise it will result in some hard to debug bug reports.
Nice catch. Will update in the next version. Thanks.
