Message ID | 20221018162117.2332508-1-zhao1.liu@linux.intel.com |
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State | New |
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Y . Srinivasan" <kys@microsoft.com>, Haiyang Zhang <haiyangz@microsoft.com>, Stephen Hemminger <sthemmin@microsoft.com>, Wei Liu <wei.liu@kernel.org>, Dexuan Cui <decui@microsoft.com>, Thomas Gleixner <tglx@linutronix.de>, Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>, Dave Hansen <dave.hansen@linux.intel.com>, x86@kernel.org, "H . Peter Anvin" <hpa@zytor.com>, linux-hyperv@vger.kernel.org, linux-kernel@vger.kernel.org Cc: Ira Weiny <ira.weiny@intel.com>, "Fabio M . De Francesco" <fmdefrancesco@gmail.com>, Zhenyu Wang <zhenyu.z.wang@intel.com>, Zhao Liu <zhao1.liu@intel.com> Subject: [PATCH] x86/hyperv: Remove BUG_ON() for kmap_local_page() Date: Wed, 19 Oct 2022 00:21:17 +0800 Message-Id: <20221018162117.2332508-1-zhao1.liu@linux.intel.com> X-Mailer: git-send-email 2.34.1 MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-Spam-Status: No, score=-4.6 required=5.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_EF,RCVD_IN_DNSWL_MED, RCVD_IN_MSPIKE_H3,RCVD_IN_MSPIKE_WL,SPF_HELO_NONE,SPF_NONE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on lindbergh.monkeyblade.net Precedence: bulk List-ID: <linux-kernel.vger.kernel.org> X-Mailing-List: linux-kernel@vger.kernel.org X-getmail-retrieved-from-mailbox: =?utf-8?q?INBOX?= X-GMAIL-THRID: =?utf-8?q?1747043721439523532?= X-GMAIL-MSGID: =?utf-8?q?1747043721439523532?= |
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x86/hyperv: Remove BUG_ON() for kmap_local_page()
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Commit Message
Zhao Liu
Oct. 18, 2022, 4:21 p.m. UTC
From: Zhao Liu <zhao1.liu@intel.com> The commit 154fb14df7a3c ("x86/hyperv: Replace kmap() with kmap_local_page()") keeps the BUG_ON() to check if kmap_local_page() fails. But in fact, kmap_local_page() always returns a valid kernel address and won't return NULL here. It will BUG on its own if it fails. [1] So directly use memcpy_to_page() which creates local mapping to copy. [1]: https://lore.kernel.org/lkml/YztFEyUA48et0yTt@iweiny-mobl/ Fixes: 154fb14df7a3 ("x86/hyperv: Replace kmap() with kmap_local_page()") Suggested-by: Fabio M. De Francesco <fmdefrancesco@gmail.com> Suggested-by: Ira Weiny <ira.weiny@intel.com> Signed-off-by: Zhao Liu <zhao1.liu@intel.com> --- arch/x86/hyperv/hv_init.c | 6 ++---- 1 file changed, 2 insertions(+), 4 deletions(-)
Comments
On Wed, Oct 19, 2022 at 12:21:17AM +0800, Zhao Liu wrote: > From: Zhao Liu <zhao1.liu@intel.com> > > The commit 154fb14df7a3c ("x86/hyperv: Replace kmap() with > kmap_local_page()") keeps the BUG_ON() to check if kmap_local_page() > fails. > > But in fact, kmap_local_page() always returns a valid kernel address > and won't return NULL here. It will BUG on its own if it fails. [1] > > So directly use memcpy_to_page() which creates local mapping to copy. > > [1]: https://lore.kernel.org/lkml/YztFEyUA48et0yTt@iweiny-mobl/ > > Fixes: 154fb14df7a3 ("x86/hyperv: Replace kmap() with kmap_local_page()") I don't know that a fixes is required here. We are not looking to backport any of this and the other patch was correct. This is just a follow on cleanup. > Suggested-by: Fabio M. De Francesco <fmdefrancesco@gmail.com> > Suggested-by: Ira Weiny <ira.weiny@intel.com> Code looks good. Without the fixes. Reviewed-by: Ira Weiny <ira.weiny@intel.com> > Signed-off-by: Zhao Liu <zhao1.liu@intel.com> > --- > arch/x86/hyperv/hv_init.c | 6 ++---- > 1 file changed, 2 insertions(+), 4 deletions(-) > > diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c > index 29774126e931..f66c5709324f 100644 > --- a/arch/x86/hyperv/hv_init.c > +++ b/arch/x86/hyperv/hv_init.c > @@ -459,13 +459,11 @@ void __init hyperv_init(void) > wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64); > > pg = vmalloc_to_page(hv_hypercall_pg); > - dst = kmap_local_page(pg); > src = memremap(hypercall_msr.guest_physical_address << PAGE_SHIFT, PAGE_SIZE, > MEMREMAP_WB); > - BUG_ON(!(src && dst)); > - memcpy(dst, src, HV_HYP_PAGE_SIZE); > + BUG_ON(!src); > + memcpy_to_page(pg, 0, src, HV_HYP_PAGE_SIZE); > memunmap(src); > - kunmap_local(dst); > } else { > hypercall_msr.guest_physical_address = vmalloc_to_pfn(hv_hypercall_pg); > wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64); > -- > 2.34.1 >
On Tue, Oct 18, 2022 at 07:58:49PM -0700, Ira Weiny wrote: > Date: Tue, 18 Oct 2022 19:58:49 -0700 > From: Ira Weiny <ira.weiny@intel.com> > Subject: Re: [PATCH] x86/hyperv: Remove BUG_ON() for kmap_local_page() > > On Wed, Oct 19, 2022 at 12:21:17AM +0800, Zhao Liu wrote: > > From: Zhao Liu <zhao1.liu@intel.com> > > > > The commit 154fb14df7a3c ("x86/hyperv: Replace kmap() with > > kmap_local_page()") keeps the BUG_ON() to check if kmap_local_page() > > fails. > > > > But in fact, kmap_local_page() always returns a valid kernel address > > and won't return NULL here. It will BUG on its own if it fails. [1] > > > > So directly use memcpy_to_page() which creates local mapping to copy. > > > > [1]: https://lore.kernel.org/lkml/YztFEyUA48et0yTt@iweiny-mobl/ > > > > Fixes: 154fb14df7a3 ("x86/hyperv: Replace kmap() with kmap_local_page()") > > I don't know that a fixes is required here. We are not looking to backport any > of this and the other patch was correct. This is just a follow on cleanup. > > > Suggested-by: Fabio M. De Francesco <fmdefrancesco@gmail.com> > > Suggested-by: Ira Weiny <ira.weiny@intel.com> > > Code looks good. Without the fixes. > > Reviewed-by: Ira Weiny <ira.weiny@intel.com> Thanks! Let me quickly refresh a v2 patch without "Fixes" tag. Zhao > > > Signed-off-by: Zhao Liu <zhao1.liu@intel.com> > > --- > > arch/x86/hyperv/hv_init.c | 6 ++---- > > 1 file changed, 2 insertions(+), 4 deletions(-) > > > > diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c > > index 29774126e931..f66c5709324f 100644 > > --- a/arch/x86/hyperv/hv_init.c > > +++ b/arch/x86/hyperv/hv_init.c > > @@ -459,13 +459,11 @@ void __init hyperv_init(void) > > wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64); > > > > pg = vmalloc_to_page(hv_hypercall_pg); > > - dst = kmap_local_page(pg); > > src = memremap(hypercall_msr.guest_physical_address << PAGE_SHIFT, PAGE_SIZE, > > MEMREMAP_WB); > > - BUG_ON(!(src && dst)); > > - memcpy(dst, src, HV_HYP_PAGE_SIZE); > > + BUG_ON(!src); > > + memcpy_to_page(pg, 0, src, HV_HYP_PAGE_SIZE); > > memunmap(src); > > - kunmap_local(dst); > > } else { > > hypercall_msr.guest_physical_address = vmalloc_to_pfn(hv_hypercall_pg); > > wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64); > > -- > > 2.34.1 > >
diff --git a/arch/x86/hyperv/hv_init.c b/arch/x86/hyperv/hv_init.c index 29774126e931..f66c5709324f 100644 --- a/arch/x86/hyperv/hv_init.c +++ b/arch/x86/hyperv/hv_init.c @@ -459,13 +459,11 @@ void __init hyperv_init(void) wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64); pg = vmalloc_to_page(hv_hypercall_pg); - dst = kmap_local_page(pg); src = memremap(hypercall_msr.guest_physical_address << PAGE_SHIFT, PAGE_SIZE, MEMREMAP_WB); - BUG_ON(!(src && dst)); - memcpy(dst, src, HV_HYP_PAGE_SIZE); + BUG_ON(!src); + memcpy_to_page(pg, 0, src, HV_HYP_PAGE_SIZE); memunmap(src); - kunmap_local(dst); } else { hypercall_msr.guest_physical_address = vmalloc_to_pfn(hv_hypercall_pg); wrmsrl(HV_X64_MSR_HYPERCALL, hypercall_msr.as_uint64);