From mboxrd@z Thu Jan 1 00:00:00 1970 Return-path: Received: from mail-eopbgr680083.outbound.protection.outlook.com ([40.107.68.83] helo=NAM04-BN3-obe.outbound.protection.outlook.com) by bombadil.infradead.org with esmtps (Exim 4.92 #3 (Red Hat Linux)) id 1i2bkg-0001VI-DM for kexec@lists.infradead.org; Tue, 27 Aug 2019 13:43:16 +0000 From: "Lendacky, Thomas" Subject: Re: [PATCH v2] x86/kdump: Reserve extra memory when SME or SEV is active Date: Tue, 27 Aug 2019 13:43:10 +0000 Message-ID: References: <20190826044535.9646-1-kasong@redhat.com> In-Reply-To: <20190826044535.9646-1-kasong@redhat.com> Content-Language: en-US Content-ID: <2DC00BA7C27A87489CB7E42FBC4B6659@namprd12.prod.outlook.com> MIME-Version: 1.0 List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "kexec" Errors-To: kexec-bounces+dwmw2=infradead.org@lists.infradead.org To: Kairui Song , "linux-kernel@vger.kernel.org" Cc: Lianbo Jiang , Baoquan He , "x86@kernel.org" , "kexec@lists.infradead.org" , Ingo Molnar , Borislav Petkov , Thomas Gleixner , Dave Young On 8/25/19 11:45 PM, Kairui Song wrote: > Since commit c7753208a94c ("x86, swiotlb: Add memory encryption support"), > SWIOTLB will be enabled even if there is less than 4G of memory when SME > is active, to support DMA of devices that not support address with the > encrypt bit. > > And commit aba2d9a6385a ("iommu/amd: Do not disable SWIOTLB if SME is > active") make the kernel keep SWIOTLB enabled even if there is an IOMMU. > > Then commit d7b417fa08d1 ("x86/mm: Add DMA support for SEV memory > encryption") will always force SWIOTLB to be enabled when SEV is active > in all cases. > > Now, when either SME or SEV is active, SWIOTLB will be force enabled, > and this is also true for kdump kernel. As a result kdump kernel will > run out of already scarce pre-reserved memory easily. > > So when SME/SEV is active, reserve extra memory for SWIOTLB to ensure > kdump kernel have enough memory, except when "crashkernel=size[KMG],high" > is specified or any offset is used. As for the high reservation case, an > extra low memory region will always be reserved and that is enough for > SWIOTLB. Else if the offset format is used, user should be fully aware > of any possible kdump kernel memory requirement and have to organize the > memory usage carefully. > > Signed-off-by: Kairui Song Reviewed-by: Tom Lendacky > > --- > Update from V1: > - Use mem_encrypt_active() instead of "sme_active() || sev_active()" > - Don't reserve extra memory when ",high" or "@offset" is used, and > don't print redundant message. > - Fix coding style problem > > arch/x86/kernel/setup.c | 31 ++++++++++++++++++++++++++++--- > 1 file changed, 28 insertions(+), 3 deletions(-) > > diff --git a/arch/x86/kernel/setup.c b/arch/x86/kernel/setup.c > index bbe35bf879f5..221beb10c55d 100644 > --- a/arch/x86/kernel/setup.c > +++ b/arch/x86/kernel/setup.c > @@ -528,7 +528,7 @@ static int __init reserve_crashkernel_low(void) > > static void __init reserve_crashkernel(void) > { > - unsigned long long crash_size, crash_base, total_mem; > + unsigned long long crash_size, crash_base, total_mem, mem_enc_req; > bool high = false; > int ret; > > @@ -550,6 +550,15 @@ static void __init reserve_crashkernel(void) > return; > } > > + /* > + * When SME/SEV is active, it will always required an extra SWIOTLB > + * region. > + */ > + if (mem_encrypt_active()) > + mem_enc_req = ALIGN(swiotlb_size_or_default(), SZ_1M); > + else > + mem_enc_req = 0; > + > /* 0 means: find the address automatically */ > if (!crash_base) { > /* > @@ -563,11 +572,19 @@ static void __init reserve_crashkernel(void) > if (!high) > crash_base = memblock_find_in_range(CRASH_ALIGN, > CRASH_ADDR_LOW_MAX, > - crash_size, CRASH_ALIGN); > - if (!crash_base) > + crash_size + mem_enc_req, > + CRASH_ALIGN); > + /* > + * For high reservation, an extra low memory for SWIOTLB will > + * always be reserved later, so no need to reserve extra > + * memory for memory encryption case here. > + */ > + if (!crash_base) { > + mem_enc_req = 0; > crash_base = memblock_find_in_range(CRASH_ALIGN, > CRASH_ADDR_HIGH_MAX, > crash_size, CRASH_ALIGN); > + } > if (!crash_base) { > pr_info("crashkernel reservation failed - No suitable area found.\n"); > return; > @@ -575,6 +592,7 @@ static void __init reserve_crashkernel(void) > } else { > unsigned long long start; > > + mem_enc_req = 0; > start = memblock_find_in_range(crash_base, > crash_base + crash_size, > crash_size, 1 << 20); > @@ -583,6 +601,13 @@ static void __init reserve_crashkernel(void) > return; > } > } > + > + if (mem_enc_req) { > + pr_info("Memory encryption is active, crashkernel needs %ldMB extra memory\n", > + (unsigned long)(mem_enc_req >> 20)); > + crash_size += mem_enc_req; > + } > + > ret = memblock_reserve(crash_base, crash_size); > if (ret) { > pr_err("%s: Error reserving crashkernel memblock.\n", __func__); > _______________________________________________ kexec mailing list kexec@lists.infradead.org http://lists.infradead.org/mailman/listinfo/kexec