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Subject[RFC PATCH 07/11] powerpc/svm: Use shared memory for Debug Trace Log (DTL)
Date
From: Anshuman Khandual <khandual@linux.vnet.ibm.com>

On Ultravisor platform kmem_cache for DTL buffers must use a constructor
function which converts the underlying buddy allocated SLUB cache pages
into shared memory so that they are accessible to the hypervisor.

Signed-off-by: Anshuman Khandual <khandual@linux.vnet.ibm.com>
Signed-off-by: Thiago Jung Bauermann <bauerman@linux.ibm.com>
---
arch/powerpc/include/asm/svm.h | 1 +
arch/powerpc/kernel/svm.c | 30 ++++++++++++++++++++++++++++++
arch/powerpc/platforms/pseries/setup.c | 5 ++++-
3 files changed, 35 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/include/asm/svm.h b/arch/powerpc/include/asm/svm.h
index 95d69e472e52..e00688761704 100644
--- a/arch/powerpc/include/asm/svm.h
+++ b/arch/powerpc/include/asm/svm.h
@@ -16,6 +16,7 @@ static bool is_svm_platform(void)

extern void mem_convert_shared(unsigned long pfn, unsigned long npages);
extern void mem_convert_secure(unsigned long pfn, unsigned long npages);
+extern void dtl_cache_ctor(void *addr);
#else
static inline bool is_svm_platform(void)
{
diff --git a/arch/powerpc/kernel/svm.c b/arch/powerpc/kernel/svm.c
index 891db2de8c04..1af5caa955f5 100644
--- a/arch/powerpc/kernel/svm.c
+++ b/arch/powerpc/kernel/svm.c
@@ -66,3 +66,33 @@ int set_memory_decrypted(unsigned long addr, int numpages)

return 0;
}
+
+/* There's one dispatch log per CPU. */
+#define NR_DTL_PAGE (DISPATCH_LOG_BYTES * CONFIG_NR_CPUS / PAGE_SIZE)
+
+static struct page *dtl_page_store[NR_DTL_PAGE];
+static long dtl_nr_pages;
+
+static bool is_dtl_page_shared(struct page *page)
+{
+ long i;
+
+ for (i = 0; i < dtl_nr_pages; i++)
+ if (dtl_page_store[i] == page)
+ return true;
+
+ return false;
+}
+
+void dtl_cache_ctor(void *addr)
+{
+ unsigned long pfn = PHYS_PFN(__pa(addr));
+ struct page *page = pfn_to_page(pfn);
+
+ if (!is_dtl_page_shared(page)) {
+ dtl_page_store[dtl_nr_pages] = page;
+ dtl_nr_pages++;
+ WARN_ON(dtl_nr_pages >= NR_DTL_PAGE);
+ mem_convert_shared(pfn, PAGE_SIZE);
+ }
+}
diff --git a/arch/powerpc/platforms/pseries/setup.c b/arch/powerpc/platforms/pseries/setup.c
index 139f0af6c3d9..50ba77c802d2 100644
--- a/arch/powerpc/platforms/pseries/setup.c
+++ b/arch/powerpc/platforms/pseries/setup.c
@@ -69,6 +69,7 @@
#include <asm/kexec.h>
#include <asm/isa-bridge.h>
#include <asm/security_features.h>
+#include <asm/svm.h>

#include "pseries.h"

@@ -288,8 +289,10 @@ static inline int alloc_dispatch_logs(void)

static int alloc_dispatch_log_kmem_cache(void)
{
+ void (*ctor)(void *) = is_svm_platform() ? dtl_cache_ctor : NULL;
+
dtl_cache = kmem_cache_create("dtl", DISPATCH_LOG_BYTES,
- DISPATCH_LOG_BYTES, 0, NULL);
+ DISPATCH_LOG_BYTES, 0, ctor);
if (!dtl_cache) {
pr_warn("Failed to create dispatch trace log buffer cache\n");
pr_warn("Stolen time statistics will be unreliable\n");
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