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X-CSE-ConnectionGUID: LYJuO2M4QVGRTFoE2AWqLg== X-CSE-MsgGUID: wC0X1+KFS260g8E7ScpCAw== X-IronPort-AV: E=McAfee;i="6800,10657,11531"; a="62800649" X-IronPort-AV: E=Sophos;i="6.17,312,1747724400"; d="scan'208";a="62800649" Received: from orviesa004.jf.intel.com ([10.64.159.144]) by orvoesa106.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 01 Sep 2025 01:55:39 -0700 X-CSE-ConnectionGUID: urilBq50To6FhMMohnQLog== X-CSE-MsgGUID: pZk/wlNJRdyHMqc/jK/2+Q== X-ExtLoop1: 1 X-IronPort-AV: E=Sophos;i="6.18,225,1751266800"; d="scan'208";a="175332922" Received: from unknown (HELO [10.238.0.107]) ([10.238.0.107]) by orviesa004-auth.jf.intel.com with ESMTP/TLS/ECDHE-RSA-AES256-GCM-SHA384; 01 Sep 2025 01:55:33 -0700 Message-ID: <281ae89b-9fc3-4a9b-87f6-26d2a96cde49@linux.intel.com> Date: Mon, 1 Sep 2025 16:55:30 +0800 Precedence: bulk X-Mailing-List: kvm@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [RFC PATCH v2 02/23] x86/virt/tdx: Add SEAMCALL wrapper tdh_mem_page_demote() To: Yan Zhao Cc: pbonzini@redhat.com, seanjc@google.com, linux-kernel@vger.kernel.org, kvm@vger.kernel.org, x86@kernel.org, rick.p.edgecombe@intel.com, dave.hansen@intel.com, kas@kernel.org, tabba@google.com, ackerleytng@google.com, quic_eberman@quicinc.com, michael.roth@amd.com, david@redhat.com, vannapurve@google.com, vbabka@suse.cz, thomas.lendacky@amd.com, pgonda@google.com, zhiquan1.li@intel.com, fan.du@intel.com, jun.miao@intel.com, ira.weiny@intel.com, isaku.yamahata@intel.com, xiaoyao.li@intel.com, chao.p.peng@intel.com References: <20250807093950.4395-1-yan.y.zhao@intel.com> <20250807094149.4467-1-yan.y.zhao@intel.com> Content-Language: en-US From: Binbin Wu In-Reply-To: <20250807094149.4467-1-yan.y.zhao@intel.com> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit On 8/7/2025 5:41 PM, Yan Zhao wrote: > From: Xiaoyao Li > > Introduce SEAMCALL wrapper tdh_mem_page_demote() to invoke the SEAMCALL > TDH_MEM_PAGE_DEMOTE, which demotes a huge leaf entry to a non-leaf entry > in the S-EPT. > > SEAMCALL TDH_MEM_PAGE_DEMOTE supports the demotion of 2MB or 1GB huge leaf > entries. > > The "gpa" and "level" parameters enable the SEAMCALL TDH_MEM_PAGE_DEMOTE to > walk the S-EPT for the huge leaf entry that needs to be demoted. > > The "page" parameter specifies a 4KB page that will be used in the demotion > operation to be added as a page table page in the S-EPT. > > Invoke tdx_clflush_page() on the 4KB page being added as a page table page. > This function performs CLFLUSH operations on certain TDX-capable platforms, > or conservatively on all TDX-capable platforms, to prevent dirty cache > lines from writing back later and corrupting TD memory. > > tdh_mem_page_demote() may fail. Callers can check function return value and > retrieve extended error info from the function output parameters "ext_err1" > and "ext_err2". e.g., due to S-EPT walk error or arriving interrupts. > > The TDX module has many internal locks. To avoid staying in SEAM mode for > too long, SEAMCALLs return a BUSY error code to the kernel instead of > spinning on the locks. Depending on the specific SEAMCALL, the caller may > need to handle this error in specific ways (e.g., retry). Therefore, return > the SEAMCALL error code directly to the caller without attempting to handle > it in the core kernel. > > Do not handle TDX_INTERRUPTED_RESTARTABLE because SEAMCALL > TDH_MEM_PAGE_DEMOTE does not check interrupts (including NMIs) for basic > TDX (with or without Dynamic PAMT). The cover letter mentions that there is a new TDX module in planning, which disables the interrupt checking. I guess TDX module would need to have a interface to report the change, KVM then decides to enable huge page support or not for TDs? > > Signed-off-by: Xiaoyao Li > Signed-off-by: Isaku Yamahata > Co-developed-by: Yan Zhao > Signed-off-by: Yan Zhao > --- > RFC v2: > - Refine the patch log (Rick). > - Do not handle TDX_INTERRUPTED_RESTARTABLE as the new TDX modules in > planning do not check interrupts for basic TDX. > > RFC v1: > - Rebased and split patch. Updated patch log. > --- > arch/x86/include/asm/tdx.h | 2 ++ > arch/x86/virt/vmx/tdx/tdx.c | 20 ++++++++++++++++++++ > arch/x86/virt/vmx/tdx/tdx.h | 1 + > 3 files changed, 23 insertions(+) > > diff --git a/arch/x86/include/asm/tdx.h b/arch/x86/include/asm/tdx.h > index f968b736871a..d2cf48e273d5 100644 > --- a/arch/x86/include/asm/tdx.h > +++ b/arch/x86/include/asm/tdx.h > @@ -178,6 +178,8 @@ u64 tdh_mng_key_config(struct tdx_td *td); > u64 tdh_mng_create(struct tdx_td *td, u16 hkid); > u64 tdh_vp_create(struct tdx_td *td, struct tdx_vp *vp); > u64 tdh_mng_rd(struct tdx_td *td, u64 field, u64 *data); > +u64 tdh_mem_page_demote(struct tdx_td *td, u64 gpa, int level, struct page *page, > + u64 *ext_err1, u64 *ext_err2); > u64 tdh_mr_extend(struct tdx_td *td, u64 gpa, u64 *ext_err1, u64 *ext_err2); > u64 tdh_mr_finalize(struct tdx_td *td); > u64 tdh_vp_flush(struct tdx_vp *vp); > diff --git a/arch/x86/virt/vmx/tdx/tdx.c b/arch/x86/virt/vmx/tdx/tdx.c > index 580f14f64822..d941f083f741 100644 > --- a/arch/x86/virt/vmx/tdx/tdx.c > +++ b/arch/x86/virt/vmx/tdx/tdx.c > @@ -1825,6 +1825,26 @@ u64 tdh_mng_rd(struct tdx_td *td, u64 field, u64 *data) > } > EXPORT_SYMBOL_GPL(tdh_mng_rd); > > +u64 tdh_mem_page_demote(struct tdx_td *td, u64 gpa, int level, struct page *page, Nit: Is it better to use a var name that clearly tell that the page is used as a table page? > + u64 *ext_err1, u64 *ext_err2) > +{ > + struct tdx_module_args args = { > + .rcx = gpa | level, > + .rdx = tdx_tdr_pa(td), > + .r8 = page_to_phys(page), > + }; > + u64 ret; > + > + tdx_clflush_page(page); > + ret = seamcall_ret(TDH_MEM_PAGE_DEMOTE, &args); > + > + *ext_err1 = args.rcx; > + *ext_err2 = args.rdx; > + > + return ret; > +} > +EXPORT_SYMBOL_GPL(tdh_mem_page_demote); > + > u64 tdh_mr_extend(struct tdx_td *td, u64 gpa, u64 *ext_err1, u64 *ext_err2) > { > struct tdx_module_args args = { > diff --git a/arch/x86/virt/vmx/tdx/tdx.h b/arch/x86/virt/vmx/tdx/tdx.h > index 096c78a1d438..a6c0fa53ece9 100644 > --- a/arch/x86/virt/vmx/tdx/tdx.h > +++ b/arch/x86/virt/vmx/tdx/tdx.h > @@ -24,6 +24,7 @@ > #define TDH_MNG_KEY_CONFIG 8 > #define TDH_MNG_CREATE 9 > #define TDH_MNG_RD 11 > +#define TDH_MEM_PAGE_DEMOTE 15 > #define TDH_MR_EXTEND 16 > #define TDH_MR_FINALIZE 17 > #define TDH_VP_FLUSH 18