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Fri, 6 Jul 2018 23:51:20 +0000 Cc: brijesh.singh@amd.com, Radim Krcmar , Peter Zijlstra , Juergen Gross , Pavel Tatashin , steven.sistare@oracle.com, daniel.m.jordan@oracle.com, x86@kernel.org, kvm@vger.kernel.org, "Lendacky, Thomas" Subject: Re: [patch 0/7] x86/kvmclock: Remove memblock dependency and further cleanups To: Paolo Bonzini , Thomas Gleixner , LKML , Borislav Petkov References: <20180706161307.733337643@linutronix.de> From: Brijesh Singh Message-ID: Date: Fri, 6 Jul 2018 18:51:16 -0500 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.13; rv:52.0) Gecko/20100101 Thunderbird/52.8.0 MIME-Version: 1.0 In-Reply-To: Content-Language: en-US X-Originating-IP: [165.204.10.251] X-ClientProxiedBy: BN4PR10CA0012.namprd10.prod.outlook.com (2603:10b6:403::22) To DM6PR12MB2682.namprd12.prod.outlook.com (2603:10b6:5:4a::31) X-MS-PublicTrafficType: Email X-MS-Office365-Filtering-Correlation-Id: bc214f1e-8950-486d-2087-08d5e39b60ef X-MS-Office365-Filtering-HT: Tenant X-Microsoft-Antispam: UriScan:; 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20:WVxU8f2Qc+CdcppacIvpoZrQBu0wVeuuvBOTfD5ArPbsQL66TUgEJ5RBxMcIe2+si7JL/aEHp2eIPwydA8hxsga+yqcXngclKVT6y8yWXJZYSsMOWtYqu/X5/+IncJoF71+lz1s5U+L57TroVP5EU9+gZ0Ah96Cppnz+uLG+kBIoYU1mh+tBuEVA+kq+qeWhwTCSouzfnfdlkLjpyHBIMNF1qC7HxhqYSyM48Wj8ZfORejpgVfrD2gDoA6Ax4onc X-OriginatorOrg: amd.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 06 Jul 2018 23:51:20.3775 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: bc214f1e-8950-486d-2087-08d5e39b60ef X-MS-Exchange-CrossTenant-FromEntityHeader: Hosted X-MS-Exchange-CrossTenant-Id: 3dd8961f-e488-4e60-8e11-a82d994e183d X-MS-Exchange-Transport-CrossTenantHeadersStamped: DM6PR12MB2682 Sender: kvm-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: kvm@vger.kernel.org X-Virus-Scanned: ClamAV using ClamSMTP Adding Tom and Boris On 7/6/18 12:47 PM, Paolo Bonzini wrote: > On 06/07/2018 18:13, Thomas Gleixner wrote: >> To allow early utilization of kvmclock it is required to remove the >> memblock dependency. memblock is currently used to allocate the per >> cpu data for kvmclock. >> >> The first patch replaces the memblock with a static array sized 64bytes * >> NR_CPUS and was posted by Pavel. That patch allocates everything statically >> which is a waste when kvmclock is not used. >> >> The rest of the series cleans up the code and converts it to per cpu >> variables but does not put the kvmclock data into the per cpu area as that >> has an issue vs. mapping the boot cpu data into the VDSO (leaks arbitrary >> data, unless page sized). >> >> The per cpu data consists of pointers to the actual data. For the boot cpu >> a page sized array is statically allocated which can be mapped into the >> VDSO. That array is used for initializing the first 64 CPU pointers. If >> there are more CPUs the pvclock data is allocated during CPU bringup. >> >> So this still will have some overhead when kvmclock is not in use, but >> bringing it down to zero would be a massive trainwreck and even more >> indirections. >> >> Thanks, >> >> tglx >> >> 8<-------------- >> a/arch/x86/include/asm/kvm_guest.h | 7 >> arch/x86/include/asm/kvm_para.h | 1 >> arch/x86/kernel/kvm.c | 14 - >> arch/x86/kernel/kvmclock.c | 262 ++++++++++++++----------------------- >> arch/x86/kernel/setup.c | 4 >> 5 files changed, 105 insertions(+), 183 deletions(-) >> >> >> >> > Thanks, this is really nice. With the small changes from my review, > > Acked-by: Paolo Bonzini Hi Paolo and Thomas, This series breaks SEV guest support. The physical address of both wall_clock and hv_clock is shared with hypervisor for updates. In case of SEV the address must be mapped as 'decrypted (i.e C=0)' so that both guest and HV can access the data correctly. The follow patch should map the pages as decrypted.         struct pvclock_vcpu_time_info *vcpu_time; @@ -269,6 +283,8 @@ void __init kvmclock_init(void)         wall_clock = (struct pvclock_wall_clock *)wall_clock_mem;         hv_clock = (struct pvclock_vsyscall_time_info *)hv_clock_mem;   +       sev_map_clocks_decrypted(); +         if (kvm_register_clock("primary cpu clock")) {                 hv_clock = NULL;                 wall_clock = NULL; But this patch triggers the below kernel crash. early_set_memory_decrypted() uses kernel_physical_mapping_init() to split the large pages and clear the C-bit. It seems this function still has dependency with memblock. [    0.000000] Hypervisor detected: KVM [    0.000000] Kernel panic - not syncing: alloc_low_pages: ran out of memory [    0.000000] CPU: 0 PID: 0 Comm: swapper Not tainted 4.18.0-rc3-sev #19 [    0.000000] Hardware name: QEMU Standard PC (Q35 + ICH9, 2009), BIOS 0.0.0 02/06/2015 [    0.000000] Call Trace: [    0.000000]  ? dump_stack+0x5c/0x80 [    0.000000]  ? panic+0xe7/0x247 [    0.000000]  ? alloc_low_pages+0x130/0x130 [    0.000000]  ? kernel_physical_mapping_init+0xe0/0x204 [    0.000000]  ? early_set_memory_enc_dec+0x10f/0x160 [    0.000000]  ? 0xffffffffb1000000 [    0.000000]  ? kvmclock_init+0x83/0x20a [    0.000000]  ? setup_arch+0x42c/0xce6 [    0.000000]  ? start_kernel+0x67/0x531 [    0.000000]  ? load_ucode_bsp+0x76/0x12e [    0.000000]  ? secondary_startup_64+0xa5/0xb0 [    0.000000] ---[ end Kernel panic - not syncing: alloc_low_pages: ran out of memory ]--- - Brijesh diff --git a/arch/x86/kernel/kvmclock.c b/arch/x86/kernel/kvmclock.c index 890e9e5..640c796 100644 --- a/arch/x86/kernel/kvmclock.c +++ b/arch/x86/kernel/kvmclock.c @@ -251,6 +251,20 @@ static void kvm_shutdown(void)         native_machine_shutdown();  }   +static void sev_map_clocks_decrypted(void) +{ +       if (!sev_active()) +               return; + +       /* +        * wall_clock and hv_clock addresses are shared with hypervisor. +        * When SEV is enabled, any addresses shared with hypervisor must be +        * mapped decrypted. +        */ +       early_set_memory_decrypted((unsigned long) wall_clock, WALL_CLOCK_SIZE); +       early_set_memory_decrypted((unsigned long) hv_clock, HV_CLOCK_SIZE); +} +  void __init kvmclock_init(void)  {