Re: [PATCH] tools/hvmloader: move shared_info to reserved memory area

[Olaf Hering <olaf@aepfle.de>]

On Fri, Oct 26, Olaf Hering wrote:

> Oh, my take would be to return false in xen_hvm_platform if the
> hypervisor is 3.3 or older, so that the guest does not use the PVonHVM
> extensions.

Like this untested patch:

diff --git a/arch/x86/xen/enlighten.c b/arch/x86/xen/enlighten.c
index 0cc41f8..8566fa8 100644
--- a/arch/x86/xen/enlighten.c
+++ b/arch/x86/xen/enlighten.c
@@ -1543,17 +1543,10 @@ static void __init xen_hvm_init_shared_info(void)
 
 static void __init init_hvm_pv_info(void)
 {
-	int major, minor;
 	uint32_t eax, ebx, ecx, edx, pages, msr, base;
 	u64 pfn;
 
 	base = xen_cpuid_base();
-	cpuid(base + 1, &eax, &ebx, &ecx, &edx);
-
-	major = eax >> 16;
-	minor = eax & 0xffff;
-	printk(KERN_INFO "Xen version %d.%d.\n", major, minor);
-
 	cpuid(base + 2, &pages, &msr, &ecx, &edx);
 
 	pfn = __pa(hypercall_page);
@@ -1604,13 +1597,29 @@ static void __init xen_hvm_guest_init(void)
 
 static bool __init xen_hvm_platform(void)
 {
+	int major, minor, old = 0;
+	uint32_t eax, ebx, ecx, edx, base;
+	bool usable = true;
+
 	if (xen_pv_domain())
 		return false;
 
-	if (!xen_cpuid_base())
+	base = xen_cpuid_base();
+	if (!base)
 		return false;
 
-	return true;
+	cpuid(base + 1, &eax, &ebx, &ecx, &edx);
+
+	major = eax >> 16;
+	minor = eax & 0xffff;
+
+	/* Require at least Xen 3.4 */
+	if (major < 3 || (major == 3 && minor < 4))
+		usable = false;
+	printk(KERN_INFO "Xen version %d.%d.%s\n",
+		major, minor, usable ? "" : " (too old)");
+
+	return usable;
 }
 
 bool xen_hvm_need_lapic(void)