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Date: Mon, 2 Aug 2021 21:18:15 +0800 From: Tianyu Lan <ltykernel@...il.com> To: Joerg Roedel <joro@...tes.org> Cc: kys@...rosoft.com, haiyangz@...rosoft.com, sthemmin@...rosoft.com, wei.liu@...nel.org, decui@...rosoft.com, tglx@...utronix.de, mingo@...hat.com, bp@...en8.de, x86@...nel.org, hpa@...or.com, dave.hansen@...ux.intel.com, luto@...nel.org, peterz@...radead.org, konrad.wilk@...cle.com, boris.ostrovsky@...cle.com, jgross@...e.com, sstabellini@...nel.org, will@...nel.org, davem@...emloft.net, kuba@...nel.org, jejb@...ux.ibm.com, martin.petersen@...cle.com, arnd@...db.de, hch@....de, m.szyprowski@...sung.com, robin.murphy@....com, thomas.lendacky@....com, brijesh.singh@....com, ardb@...nel.org, Tianyu.Lan@...rosoft.com, rientjes@...gle.com, martin.b.radev@...il.com, akpm@...ux-foundation.org, rppt@...nel.org, kirill.shutemov@...ux.intel.com, aneesh.kumar@...ux.ibm.com, krish.sadhukhan@...cle.com, saravanand@...com, xen-devel@...ts.xenproject.org, pgonda@...gle.com, david@...hat.com, keescook@...omium.org, hannes@...xchg.org, sfr@...b.auug.org.au, michael.h.kelley@...rosoft.com, iommu@...ts.linux-foundation.org, linux-arch@...r.kernel.org, linux-hyperv@...r.kernel.org, linux-kernel@...r.kernel.org, linux-scsi@...r.kernel.org, netdev@...r.kernel.org, vkuznets@...hat.com, anparri@...rosoft.com Subject: Re: [PATCH 05/13] HV: Add Write/Read MSR registers via ghcb page On 8/2/2021 8:28 PM, Joerg Roedel wrote: > On Wed, Jul 28, 2021 at 10:52:20AM -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; >> + >> + WARN_ON(in_nmi()); >> + >> + 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); > > Do you really need to zero out the whole 4k? The validation bitmap > should be enough, there are no secrets on the page anyway. > Same in hv_ghcb_msr_read(). OK. Thanks for suggestion. I will have a try. > >> +enum es_result sev_es_ghcb_hv_call(struct ghcb *ghcb, >> + struct es_em_ctxt *ctxt, >> + u64 exit_code, u64 exit_info_1, >> + u64 exit_info_2) >> { >> enum es_result ret; >> >> @@ -109,7 +109,16 @@ static enum es_result sev_es_ghcb_hv_call(struct ghcb *ghcb, >> ghcb_set_sw_exit_info_1(ghcb, exit_info_1); >> ghcb_set_sw_exit_info_2(ghcb, exit_info_2); >> >> - sev_es_wr_ghcb_msr(__pa(ghcb)); >> + /* >> + * Hyper-V runs paravisor with SEV. Ghcb page is allocated by >> + * paravisor and not needs to be updated in the Linux guest. >> + * Otherwise, the ghcb page's PA reported by paravisor is above >> + * VTOM. Hyper-V use this function with NULL for ctxt point and >> + * skip setting ghcb page in such case. >> + */ >> + if (ctxt) >> + sev_es_wr_ghcb_msr(__pa(ghcb)); > > No, do not make this function work with ctxt==NULL. Instead, factor out > a helper function which contains what Hyper-V needs and use that in > sev_es_ghcb_hv_call() and Hyper-V code. > OK. Will update. >> +union hv_ghcb { >> + struct ghcb ghcb; >> +} __packed __aligned(PAGE_SIZE); > > I am curious what this will end up being good for. > Hyper-V introduces a specific hypercall request in GHCB page and use same union in the Linux Hyper-V code to read/write MSR and call the new hypercall request.
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