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arch-x86, cpu-kvm: initialize x87 FCW (#877)

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Fix #876. The x87 floating-point control word (FCW) was not initialized
at process startup in syscall emulation mode. This resulted in floating
point exceptions in KVM mode when executing x87 floating-point
instructions.

This patch fixes the bug by initializing FCW to its reset value, 0x37F.

Change-Id: Idd1573c6951524ef59466cc5c9f1e640ea7658ae
This commit is contained in:
Nicholas Mosier
2024-02-20 07:46:44 -08:00
committed by GitHub
parent 4e75e35a33
commit 7ac9733199
1 changed files with 3 additions and 0 deletions
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3
src/arch/x86/process.cc
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@@ -398,6 +398,7 @@ X86_64Process::initState()
tc->setMiscReg(misc_reg::Mxcsr, 0x1f80);
tc->setMiscReg(misc_reg::Ftw, 0xffff);
tc->setMiscReg(misc_reg::Fcw, 0x037f);
tc->setMiscReg(misc_reg::ApicBase, 0xfee00900);
@@ -617,6 +618,7 @@ X86_64Process::initState()
tc->setMiscReg(misc_reg::Mxcsr, 0x1f80);
tc->setMiscReg(misc_reg::Ftw, 0xffff);
tc->setMiscReg(misc_reg::Fcw, 0x037f);
// Setting CR3 to the process pid so that concatinated
// page addr with lower 12 bits of CR3 can be used in SE
@@ -752,6 +754,7 @@ I386Process::initState()
tc->setMiscReg(misc_reg::Mxcsr, 0x1f80);
tc->setMiscReg(misc_reg::Ftw, 0xffff);
tc->setMiscReg(misc_reg::Fcw, 0x037f);
}
}