linux-kernel - [PATCH v2 08/13] powerpc/pseries/svm: Unshare all pages before kexecing a new kernel

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Message-Id: <20190713060023.8479-9-bauerman@linux.ibm.com>
Date:   Sat, 13 Jul 2019 03:00:18 -0300
From:   Thiago Jung Bauermann <bauerman@...ux.ibm.com>
To:     linuxppc-dev@...ts.ozlabs.org
Cc:     linux-kernel@...r.kernel.org, Alexey Kardashevskiy <aik@...abs.ru>,
        Anshuman Khandual <anshuman.linux@...il.com>,
        Benjamin Herrenschmidt <benh@...nel.crashing.org>,
        Christoph Hellwig <hch@....de>,
        Michael Ellerman <mpe@...erman.id.au>,
        Mike Anderson <andmike@...ux.ibm.com>,
        Paul Mackerras <paulus@...ba.org>,
        Ram Pai <linuxram@...ibm.com>,
        Claudio Carvalho <cclaudio@...ux.ibm.com>,
        Thiago Jung Bauermann <bauerman@...ux.ibm.com>
Subject: [PATCH v2 08/13] powerpc/pseries/svm: Unshare all pages before kexecing a new kernel

From: Ram Pai <linuxram@...ibm.com>

A new kernel deserves a clean slate. Any pages shared with the hypervisor
is unshared before invoking the new kernel. However there are exceptions.
If the new kernel is invoked to dump the current kernel, or if there is a
explicit request to preserve the state of the current kernel, unsharing
of pages is skipped.

NOTE: While testing crashkernel, make sure at least 256M is reserved for
crashkernel. Otherwise SWIOTLB allocation will fail and crash kernel will
fail to boot.

Signed-off-by: Ram Pai <linuxram@...ibm.com>
Signed-off-by: Thiago Jung Bauermann <bauerman@...ux.ibm.com>
---
 arch/powerpc/include/asm/ultravisor-api.h | 1 +
 arch/powerpc/include/asm/ultravisor.h     | 6 ++++++
 arch/powerpc/kernel/machine_kexec_64.c    | 8 ++++++++
 3 files changed, 15 insertions(+)

diff --git a/arch/powerpc/include/asm/ultravisor-api.h b/arch/powerpc/include/asm/ultravisor-api.h
index c7513bbadf57..ab4f756cb91c 100644
--- a/arch/powerpc/include/asm/ultravisor-api.h
+++ b/arch/powerpc/include/asm/ultravisor-api.h
@@ -29,5 +29,6 @@
 #define UV_UNSHARE_PAGE			0xF134
 #define UV_PAGE_INVAL			0xF138
 #define UV_SVM_TERMINATE		0xF13C
+#define UV_UNSHARE_ALL_PAGES		0xF140
 
 #endif /* _ASM_POWERPC_ULTRAVISOR_API_H */
diff --git a/arch/powerpc/include/asm/ultravisor.h b/arch/powerpc/include/asm/ultravisor.h
index f7418b663a0e..80d4beaf61b8 100644
--- a/arch/powerpc/include/asm/ultravisor.h
+++ b/arch/powerpc/include/asm/ultravisor.h
@@ -106,6 +106,12 @@ static inline int uv_unshare_page(u64 pfn, u64 npages)
 	return ucall(UV_UNSHARE_PAGE, retbuf, pfn, npages);
 }
 
+static inline int uv_unshare_all_pages(void)
+{
+	unsigned long retbuf[UCALL_BUFSIZE];
+
+	return ucall(UV_UNSHARE_ALL_PAGES, retbuf);
+}
 #endif /* !__ASSEMBLY__ */
 
 #endif	/* _ASM_POWERPC_ULTRAVISOR_H */
diff --git a/arch/powerpc/kernel/machine_kexec_64.c b/arch/powerpc/kernel/machine_kexec_64.c
index 75692c327ba0..b3d87d32e8f7 100644
--- a/arch/powerpc/kernel/machine_kexec_64.c
+++ b/arch/powerpc/kernel/machine_kexec_64.c
@@ -31,6 +31,7 @@
 #include <asm/smp.h>
 #include <asm/hw_breakpoint.h>
 #include <asm/asm-prototypes.h>
+#include <asm/ultravisor.h>
 
 int default_machine_kexec_prepare(struct kimage *image)
 {
@@ -329,6 +330,13 @@ void default_machine_kexec(struct kimage *image)
 #ifdef CONFIG_PPC_PSERIES
 	kexec_paca.lppaca_ptr = NULL;
 #endif
+
+	if (is_secure_guest() && !(image->preserve_context ||
+				   image->type == KEXEC_TYPE_CRASH)) {
+		uv_unshare_all_pages();
+		printk("kexec: Unshared all shared pages.\n");
+	}
+
 	paca_ptrs[kexec_paca.paca_index] = &kexec_paca;
 
 	setup_paca(&kexec_paca);